Patent Publication Number: US-11044314-B2

Title: System and method for a database proxy

Description:
RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 15/344,993, filed Nov. 7, 2016, and claims priority to U.S. Provisional Patent Application No. 62/319,223, filed Apr. 6, 2016 and U.S. Provisional Patent Application No. 62/383,297, filed Sep. 2, 2016. Each of which are hereby incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to computing systems and the use of proxy technology between an application server and a database server/store. 
     BACKGROUND 
     Data center architecture has been evolving rapidly over the last decade. This includes changes to the data center architecture for systems including one or more NoSQL data servers (also referred to as NoSQL data stores). Each customer can have different data center architectures for specific application(s). 
     Typically there are four tiers in a data center architecture that also uses a NoSQL data store. The four tiers are: web tier comprising front end web servers, application tier comprising application servers, data tier comprising database servers, and storage tier.  FIG. 1  shows a typical architecture of data center for an Internet company (e.g., Yahoo, LinkedIn, eBay, etc.) comprising the four tiers. The dotted lines separate different tiers of servers based on their functional attributes related to specific data center architecture. 
     In the data center architecture of  FIG. 1 , the application servers are responsible for running the business or application logic. The storage tier is accessed via database servers, such as the NoSQL servers of  FIG. 1 . These NoSQL servers act as access medium to the NoSQL data stores. Application logic accesses the NoSQL data store to manage data. Below are the typical steps involved in retrieving required (READ operation) data from a data store:
         1. Application logic wants a specific data that is associated with a key. The application, for example, speaks JavaScript Object Notation (JSON).   2. Application will open a connection to the NoSQL data server and request the data associated with that key.   3. If the NoSQL data server speaks another format, e.g., Binary JSON (BSON), then application server needs to convert its request to BSON first (or NoSQL server needs to parse JSON).   4. The NoSQL server will now check if the data associated with the key is available in its local cache, if not it will fetch it from the persistent storage.   5. In case NoSQL server has to fetch from the persistent storage, it needs to resolve if the key points to a secondary index or primary index. If it is a secondary index, then it needs to be converted to primary index.   6. Finally the data is now retrieved either from local cache or persistent storage and returned to the application logic.       

     This approach suffers from several possible bottlenecks that limit efficient scaling of application deployment using NoSQL data stores. Accordingly, improved approaches to the NoSQL data center architecture are desirable. 
     SUMMARY 
     According to some embodiments a NoSQL proxy includes a packet processor for exchanging messages over a network with one or more application servers, NoSQL data stores, and peer NoSQL proxies, a proxy finite state machine for managing data access commands received by the NoSQL proxy, an interface for accessing cached data in a hybrid memory management unit, and a data access command processing unit for translating secondary indexes to primary indexes, translating data between data formats, and evaluating and filtering data access command results. The NoSQL proxy is configured to receive a data access command, process the data access command using cached data when data associated with the data access command is cached locally, forward the data access command to the one of the peer NoSQL proxies when the data is cached in the one of the peer NoSQL proxies, forward the data access command to one of the NoSQL data stores when the data is not cached or changes to the data are written through to the one of the NoSQL data stores, and return results of the data access command. 
     According to some embodiments, a database proxy includes a request processor, a cache coupled to the request processor, a database plugin coupled to the request processor, a first interface for coupling the request processor to one or more client devices, a second interface for coupling the request processor to one or more other database proxies, and a third interface for coupling the database plugin to one or more database servers. The request processor is configured to receive a database read request from a client using the first interface, determine whether the database read request is assigned to the database proxy, and return results of the database read request to the client using the first interface. When the database read request is not assigned to the database proxy, the request processor is configured forward the database read request to a first one of the one or more other database proxies using the second interface. When the database read request is assigned to the database proxy, the request processor is configured to process the database read request using data stored in the cache when data associated with the database read request is stored in the cache and forward the database read request to the database plugin when the data associated with the database read request is not stored in the cache and store results of the database read request received from the database plugin in the cache. The database plugin is configured to forward the database read request to a first one of the one or more database servers, receive the results of the database read request from the first one of the one or more database servers, and return the results to the request processor. 
     According to some embodiments, a method of processing database read requests using database proxies includes a request processor of a first database proxy receiving a database read request from a client using a first interface, determining whether the database read request is assigned to the first database proxy, and returning results of the database read request to the client using the first interface. When the database read request is not assigned to the first database proxy, the method further includes the request processor forwarding the database read request to a second database proxy using a second interface. When the database read request is assigned to the first database proxy, the method further includes processing, by the request processor, the database read request using data stored in a cache when data associated with the database read request is stored in the cache and forwarding, by a database plugin of the first database proxy, the database read request to a database server and storing, by the request processor, results of the database read request received from the database plugin in the cache when the data associated with the database read request is not stored in the cache. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified diagram of a typical data center architecture according to some embodiments. 
         FIG. 2  is a simplified diagram of a NoSQL data server/store use case according to some embodiments. 
         FIG. 3  is a simplified diagram of a NoSQL Proxy within an existing data center architecture according to some embodiments. 
         FIG. 4  is a simplified diagram of a data center architecture with a NoSQL proxy in the database server according to some embodiments. 
         FIG. 5  is a simplified diagram of a data center architecture with a NoSQL proxy in the application server according to some embodiments. 
         FIG. 6  is a simplified diagram of a data center architecture with a NoSQL proxy in the database server that supports a native application programming interface according to some embodiments. 
         FIG. 7  is a simplified diagram of a method of connection establishment between a NoSQL proxy and an application server as well as a NoSQL data server according to some embodiments. 
         FIG. 8  is a simplified diagram of a method of performing CRUD operations using a NoSQL Proxy according to some embodiments. 
         FIG. 9  is a simplified diagram of an internal architecture for a NoSQL proxy according to some embodiments. 
         FIG. 10  is a simplified diagram of a data center architecture using database proxies according to some embodiments. 
         FIG. 11  is a simplified diagram of a method of handling read requests using database proxies according to some embodiments. 
         FIG. 12  is a simplified diagram of a method of handling update, write, or delete requests using database proxies according to some embodiments. 
     
    
    
     In the figures, elements having the same designations have the same or similar functions. 
     DETAILED DESCRIPTION 
     In the following description, specific details are set forth describing some embodiments consistent with the present disclosure. It will be apparent, however, to one skilled in the art that some embodiments may be practiced without some or all of these specific details. The specific embodiments disclosed herein are meant to be illustrative but not limiting. One skilled in the art may realize other elements that, although not specifically described here, are within the scope and the spirit of this disclosure. In addition, to avoid unnecessary repetition, one or more features shown and described in association with one embodiment may be incorporated into other embodiments unless specifically described otherwise or if the one or more features would make an embodiment non-functional. 
       FIG. 2  shows a sub-set view of the data center architecture in  FIG. 1 .  FIG. 2  helps illustrate points in the architecture where challenges exist. 
     In  FIG. 2 , notice the use of representational state transfer (REST) application programming interface (API) on the application servers in conjunction with a container based deployment. Many NoSQL data stores support four main operations, CREATE, READ, UPDATE, and DELETE, represented using the acronym CRUD. As described below, the various embodiments are orthogonal to container technology and will work with both containers and virtual machine (VM)-based deployment models as well as with bare metal servers without the use of containers or VMs. Performance is typically measured using two main metrics for NoSQL data stores: first, throughput is measured using transactions per second (TPS), and second, latency of data access between application server and NoSQL data store. In some examples, performance measured by these or other metrics is typically provided according to a system-level agreement (SLA). 
       FIG. 2  further illustrates a REST API, however this does not preclude a native API based solution in the context of the described embodiments. 
     There are several possible bottlenecks and limitations that limit efficient scaling of application deployment using NoSQL data stores having the architecture shown in  FIG. 2 .
         1. Connection scatter-gather: As seen in  FIG. 2 , there is an explosion of network connections between the application server and the NoSQL data server. Thus both the application server and the NoSQL data server are asked to support a lot of network connections, more so for NoSQL data server. This usually impacts the latency of accesses between application server and NoSQL data store (SLA).   2. Need for increased operating data set: Operating data set is an important criterion for exploiting data locality. An operating data set for a NoSQL data store is the data set and its neighboring data sets (or related data sets) that are currently being processed. In embodiments of the architecture, the operating data set is limited by the available memory on the NoSQL data server. Adding SSD Flash memory is an option but it will take away useful cycles from the NoSQL data server towards managing the Flash memory.   3. Data serialization and deserialization (serdes): Given the applications use a different serialization protocol and the NoSQL data stores use a different one, additional processing is performed either in the NoSQL data server or on the application server. This results in lower throughput (TPS).   4. Converting secondary index to primary index: For data that is retrieved from the persistent storage, the NoSQL data server often has to convert the secondary index to primary index. For example, in some of the larger installations, customers end up using a secondary non-blocking specialized indexing engine to lookup the primary indexes associated with a secondary index (e.g., Espresso at LinkedIn uses Lucene for secondary index lookup). Typically there is a degradation of 5-10% in performance on the write throughput. However, as described below, the secondary indexing engine is optional and may be omitted in the described embodiments.   5. Management of compression, decompression, encryption, security, and/or other related protocols may often have a negative impact on throughput, etc. as processor and other computing resources are often dedicated to these tasks.   6. Business continuity: When an unforeseen event brings the NoSQL data server down, a service that can serve the applications with required data from a duplicate store is also advantageous.       

     Scaling NoSQL data stores to serve millions (and millions) of transactions often involves adding many CPU servers both to the application tier as well as to the NoSQL data tier. This makes the scaling of NoSQL data stores highly inefficient. 
     Several approaches may be used to create scalable NoSQL data stores. These approaches include: adding a caching tier (e.g. memcached, etc.) using commodity servers with larger memory, using a pool of connections in the application server to talk to NoSQL data store, thus using a fixed number of connections and writing a scheduler to manage data over these connections, and a NoSQL proxy, without a cache, implemented in the application server to reduce the number of connections to the caching tier. These methods rely on a separate caching (or memory) tier. To support large addressable memory space in an efficient manner, one needs a tiered memory architecture that can support SRAM, DRAM, and Flash memories. 
     The NoSQL proxy in the embodiments described below supports a tiered memory architecture. The above methods support a native wire protocol such as memcached, etc. to keep the protocol overhead minimal at the cost of less flexibility in the application logic. Supporting REST interface allows application logic to be flexible to migrate to another NoSQL data store if necessary. In some example, the NoSQL proxy proposed here supports a REST interface, since the efficient REST implementation results in a negligible overhead. Finally, a high throughput and low latency packet processor enables supporting different network bandwidths at the network interface (e.g. Ethernet interface). For example, NoSQL proxy can support, 1 Gb/s to 40 Gb/s in the same architecture. 
     To address the above challenges, a NoSQL Proxy that provides an efficient solution to scale additional traffic between application servers and NoSQL data servers is desirable. As described below, several embodiments of a NoSQL Proxy address these challenges. 
     A NoSQL Proxy is a proxy that sits between an application server and a NoSQL data server. Its primary function is to act as a proxy for the underlying NoSQL data store, while supporting a REST API. The application logic interacts with the NoSQL Proxy&#39;s REST API without the knowledge of the specific NoSQL data store underneath.  FIG. 3  illustrates the use of NoSQL Proxy based on the architecture used in  FIG. 2 . Notice that the NoSQL Proxy can reside in either the NoSQL data server or the application server. The implications of where the NoSQL proxy resides on the scaling as well as its ability to address the challenges identified earlier are described in further detail below. 
     The NoSQL Proxy is a proxy that allows for efficient scaling of traffic between application servers and NoSQL data servers. The features of the NoSQL Proxy that allow the NoSQL proxy to scale to millions of low latency transactions are listed below. As Moore&#39;s law scales the gains will scale accordingly.
         High throughput—millions of transactions/sec (e.g. up to 10 M TPS)   Network IO—high fan out, low-latency packet processor
           Up to 10,000 TCP connections with &lt;1 ms latency per connection   
           Flexibility to configure the size of key-value (KV) store or the cache
           Terabytes of data store (e.g., up to 4 TB) using tiered memory   
           Line-rate data serialization and deserialization
           Support for multiple data serialization/deserialization (serdes) formats (JSON, BSON, Protobuf, . . . )   
           Line-rate secondary index to primary index conversion   Full control over how data is managed with a powerful default
           Persistence of data supported via configuration API (both dynamic and static)   Ability to expire/expel any amount of data in store (data flush)   No replication of cache data in case of deployment in application servers
               Networked interface to query other Proxies on application servers   
               
           High availability—operational even when NoSQL data server goes down   REST API for application logic       

     An exemplary use case when the NoSQL Proxy resides in the NoSQL data server is shown in  FIG. 4 . In this use case, a typical call sequence is as follows:
         1. Application logic maintains a pool of connections open to the NoSQL Proxy. When the application logic needs to retrieve specific data, it requests the data using the associated key and using a REST API (as described later in the document) supported by the NoSQL Proxy.   2. The NoSQL Proxy reads the REST API and checks if the requested key is available in the local cache of the NoSQL Proxy, and if it is, then it returns the data in the appropriate data format. If the key is not available in the cache, the NoSQL Proxy checks if the key points to a secondary index, if so then it converts the secondary index to primary index and then retrieves corresponding data from the persistent NoSQL store. The NoSQL Proxy then returns the data back to the application logic while adding it to the local cache and updating the Least Recently Used (LRU) tag.       

     It is helpful to note that the NoSQL Proxy is performing various computational steps such as network connection management, data serdes, and conversion of secondary to primary index. Thus, relieving the NoSQL data server of these tasks. 
     An exemplary use case when the NoSQL Proxy resides in the application server and uses a REST API is shown in  FIG. 5 . In this use case, a typical call sequence is as follows:
         1. Application logic maintains a pool of connections open to the NoSQL proxy. The application logic talks to the Proxy via a REST API (can be implemented over PCIe link as needed). When the application logic uses a specific data format, it requests the NoSQL Proxy for the same.   2. The NoSQL Proxy in turn looks up if the data is available in the cache or in any other peer Proxy or it locates the target NoSQL data server from which to request the data. Once the location of data is identified, the NoSQL Proxy will retrieve data and return it back to the application logic. Similar to the earlier use case, the Proxy will perform secondary to primary index conversion as well as data serdes.       

     In this use scenario, the NoSQL Proxy has lower latency since the NoSQL Proxy is close to the application logic avoiding additional hops to a top of the rack (TOR) switch, etc. 
     An exemplary use case when the NoSQL Proxy resides in the NoSQL data server and uses a native API is shown in  FIG. 6 . The typical call sequence for the NoSQL Proxy of  FIG. 6  is similar to the call sequence for the NoSQL Proxy of  FIG. 4  with the exception of the use of a native API rather than a REST API. 
       FIG. 7  is a simplified diagram of a method of connection establishment between a NoSQL proxy and an application server as well a NoSQL data server according to some embodiments. As shown in  FIG. 7 , the NoSQL Proxy is able to support connection management between the application server and the NoSQL server by monitoring the number of connections between the application server and the NoSQL server. 
       FIG. 8  is a simplified diagram of a method of performing CRUD operations using a NoSQL Proxy according to some embodiments. As shown in  FIG. 8 , commands are handled based on the type of command (CREATE, READ, UPDATE, and/or DELETE) and where the data associated with the command is located. When the command is a CREATE command, the NoSQL Proxy creates and stores the new data in its local data store and then passes the CREATE command to the NoSQL data store using a write through strategy. When the command is a READ, UPDATE, or DELETE command, the NoSQL Proxy first checks whether the associated data is cached locally. When the data is cached locally, the READ command is handled directly by returning the copy of the data from the local data store. When the data is cached locally, the UPDATE and DELETE commands are handled directly by making changes in the local data store and then the command is forwarded to the NoSQL data store to make the respective update or delete in the NoSQL data store copy of the data. When the data is not cached locally, the NoSQL Proxy checks to see if a peer NoSQL Proxy has cached the data. When the data is cached by a peer NoSQL Proxy, the command is forwarded to the peer NoSQL Proxy for handling. When the data is not cached locally or in a peer NoSQL Proxy, the command is passed to the NoSQL data store for handling. In some examples, when READ and/or UPDATE are forwarded to the NoSQL data store when the data is not cached locally, the data read and/or update may be cached locally to support future commands using that data. 
       FIG. 9  is a simplified diagram of an internal architecture for a NoSQL Proxy according to some embodiments. The NoSQL Proxy may be implemented using any suitable combination of one or more central processing units, processors, multi-core processors, microprocessors, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), systems on a chip (SOCs), off the shelf components, boards, and/or the like; including, for example, a combination of one or more central processing units and FPGAs, a combination of one or more FPGAs and SOCs, and/or the like. As shown in  FIG. 9 , the NoSQL Proxy includes the following subsystems:
         1. the 10 sub-system includes a 10 GbE MAC, a hybrid memory controller interfacing with DDR3 DRAM memory and SSD Flash memory, and a PCIe 3.0 interface. In some examples, this sub-system is implemented in Verilog. Depending upon whether the NoSQL Proxy is located in the application server or the NoSQL data store, data commands to be processed by the NoSQL Proxy may be received via the PCIe interface and/or the network via the 10 GbE MAC.   2. the packet processor manages Ethernet and TCP/IP connections with, for example, a Linux server. In some examples, the packet processor may be implemented in C and is operable with a standard Linux distribution, such as CentOS as well as on FPGA. The packet processor supports IPv4, TCP, DHCP, ARP, ICMP protocols. A suitable packet processor is described further in U.S. Patent Application Ser. No. 62/681,922, titled “Bid Gateway for a Real-time Ad Bidding” and filed in January 2016, which is hereby incorporated by reference in its entirety.   3. a secure REST interface includes a HTTP engine and an SSL engine. In some examples, in this sub-system, a REST interface encoder and decoder are implemented based on a HTTP engine. In some examples, the REST interface supports SSL encoding and decoding for secure data exchange.   4. a data serdes engine supports various serdes protocols (e.g., JSON, ProtoBuf, Thrift, etc.). The data serdes engine allows for instantiating various serdes protocols with an ability to do protocol translation at line-rate. For example, the incoming data requests can be in JSON, whereas the NoSQL data server returns data in BSON or Thrift. The data serdes engine will perform data format translation and return back valid JSON data to the application logic.   5. an index converter provides support for line rate translation of secondary indices included as part of data request to primary indices. This allows the data request to be completed using the more efficient primary indices.   6. a Proxy finite state machine (FSM) that comprises a FSM to manage various data and control transactions. The Proxy FSM keeps track of the state information of the NoSQL Proxy on a per-transaction basis and/or on a per-connection basis. It also interfaces with the configuration and coordination engine as well as the load balancer to determine appropriate actions (e.g., forwarding requests to another peer NoSQL Proxy).   7. a configuration and coordination engine that manages consensus and coordination among the sub-systems and/or other peer NoSQL Proxies operating in cooperation with the current NoSQL Proxy. Usually there is a trade-off between accepting data loss or delay or inconsistency and devoting more CPU cycles and network bandwidth to this function. One of the blocks in the configuration and coordination engine that can be accelerated and made highly efficient is the atomic broadcast (at the leader side) and the register and response block (at the follower side). In some examples, these improvements are implemented in the configuration and coordination engine so that scaling to more NoSQL Proxies becomes efficient. In some examples, the configuration and coordination engine operates using the Apache ZooKeeper project. In some examples, Zookeeper is used for consensus and coordination of status and functional upkeep information (e.g., service is at w.x.y.z IP address, supports xxx Mb/s traffic, service is up, etc.). In some examples, Zookeeper is not for general data sharing between NoSQL Proxies, which occurs over the network interface.   8. a load balancer to interface with other peer NoSQL Proxy instances to better manage the application side traffic. In some examples, the load balancer maintains a set of counters and logic to measure a targeted metric (e.g., transactions per second, Mb/s or Gb/s, and/or the like) and decides whether a particular peer NoSQL Proxy is running at a load higher than a present number (e.g., 85%, 90%, and/or the like). In some examples, when it appears based on the targeted metric that a NoSQL Proxy is likely not going to be able to meet the set SLA, an incoming request for a transaction is forwarded to another peer NoSQL Proxy that has more capacity to handle the request. In some examples, bloom filters and/or the like are used to determine as a pre-processing step to load balancing whether the data for the incoming request being analyzed is cached in the current NoSQL Proxy. When the data is not cached locally, the request becomes subject to load balancing and may be forwarded to a peer NoSQL Proxy that has capacity to do further calculations and handle the request.   9. a hybrid memory management unit (H-MMU) that allows a flexible caching strategy where data may be stored using a combination of DRAM and SSD. In some examples, this allows access to cached data at DRAM latencies while allowing the H-MMU to determine appropriate reading and/or writing schedules to the SSD. In some examples, the H-MMU may also enable isolation of either DRAM or SRAM from SSD, so that data may be cached directly in SSD without also being cached in SRAM or DRAM. In some examples, this isolation supports the writing of temporary data to SRAM and not allowing other permanent data from polluting the SRAM that is crucial to achieving performance. In some examples, the bloom filter tables/vectors may be stored in the SRAM and perform fast checks on whether the said proxy has the specific data or not. Architecture and operation of embodiments of the H-MMU is further described in U.S. Pat. No. 9,286,221, which is hereby incorporated by reference in its entirety.   10. a compute block that supports regular expression (regex) evaluation, filtering, and/or the like. In some examples, the compute block supports libraries capable of extending a language framework such as node.js. In some examples, the compute block supports tight coupling with one or more processors on the FPGA and/or accessible to the NoSQL Proxy via the PCIe interface, and/or other interfaces. In some examples, an interface, such as QuickPath Interconnect (QPI) from Intel Corporation, accelerator coherence port (ACP) from ARM Ltd., Coherent Accelerator Processor Interface (CAPI) from IBM, and/or the like, allows data moves between the NoSQL Proxy and the one or more processors using L2/L3 cache and not via the PCIe bus. In some examples, a compilation of a domain-specific language, such as Ragel and/or the like, may be used to support descriptions of complex data filtering and classing using regular expressions, that will generate C code for operation on the one or more processors or that can alternative be compiled into an FPGA using a high-level synthesis compiler.       

     According to some embodiments, the NoSQL Proxy may receive a data command from application logic via the PCIe interface when the NoSQL Proxy is located in the application server or via the 10 GbE MAC network interface from either an application server (e.g., when the NoSQL Proxy is located in either the application server or the NoSQL data store) or from a peer NoSQL Proxy when the NoSQL Proxy has cached data for a command received by the peer NoSQL Proxy (e.g., as described in  FIG. 8 ). In some examples, the command is then forwarded to the index converter so that data references in the command that each reference to a secondary index is converted to a corresponding primary index to make the ensuing data access requests more efficient. In some examples, the index conversion occurs as line rate so as not to introduce unwanted delays in the processing of the command. In some examples, the command is then passed to the data serdes engine to convert data in the command to the data format protocol of the NoSQL data store. In some examples, the protocol conversion occurs as line rate so as not to introduce unwanted delays in the processing of the command. The command is then processed using, for example, the method of  FIG. 8 . In some examples, the results of the command are then passed through a compute block for additional processing to support additional expression evaluation and/or filtering. In some examples, results of the command are then passed back through a data serdes engine to convert the results to the data format protocol of the application logic issuing the command. In some examples, the protocol conversion occurs as line rate so as not to introduce unwanted delays in the processing of the command. The results of the command are then passed back to the application logic. 
       FIG. 10  is a simplified diagram of a data center architecture  100  using database proxies according to some embodiments. As shown in  FIG. 10 , data center architecture  100  is built around a multi-tier client-service model consistent with the data center architectures of  FIGS. 1-6 . Data center architecture  100  includes a client  110 . And although only one client is shown in  FIG. 10 , data center architecture  100  may include any number of clients similar and/or different from client  110 . In some embodiments, client  110  is consistent with the application servers of  FIGS. 1-6 . And although not shown in  FIG. 10 , client  110  may include one or more processors, memory, operating systems, virtual machines, and/or the like as would be understood by one of ordinary skill. As shown, client  110  includes an application  111 , a client-side driver  112 , and a network interface  113 . Application  111  is representative of any of many possible applications that may need the storage services of a database and may correspond to an end-user application, an application in an application tier supporting a front end server, and/or the like. 
     Application  111  uses client-side driver  112  to take advantage of the database proxies in data center architecture  100 . In some examples, client-side driver  112  may include an API that acts as an interface, such as a facade interface, between application  111  and the database proxies of data center architecture  100 . In some examples, client-side driver  112  may provide access to functions typically found in database driver interfaces including support for functions such as query manipulation, connection management, authentication, query submission, query results handling, transactions, and/or the like. In some examples, the functionality of the client-side driver may be implemented as a REST API and/or a native API. In some examples, client-side driver  112  may be used in place of or as a supplement to one or more other database drivers usable by application  111  to access one or more database servers in data center architecture  100 . In some examples, client-side driver  112  may also provide support for connection pooling between client  110  and the database proxies of data center architecture  100  so that when a communication connection between client  110  and a database proxy is requested, an existing connection in the connection pool may be used immediately without incurring the delay of establishing a new connection. 
     Network interface  113  provides connectivity between client  110  and/or client-side driver  112  and a network  120 . Network  120  may correspond to any type of network including a local area network (such as an Ethernet), a wireless network, a data center network, a wide area network (such as the internet), and/or the like. Network  120  may include any number of network switching devices, bridges, hubs, routers, access points, gateways, and/or the like. Network interface  113  may include a combination of software drivers, firmware, hardware modules, and/or the like that provide network access and network services as would be expected in a network driver providing support for layered network systems such as TCP/IP, OSI, and/or the like. In some examples, network interface  113  may include physical layer support, medium access control (e.g., Ethernet, and/or the like), access to routing services (e.g., IP), access to delivery services (e.g., TCP, UDP, and/or the like), support for network management (e.g., ICMP, ARP, DHCP, and/or the like), one or more packet processors, one or more queues, one or more application layer APIs (e.g., HTTP, other REST APIs, and/or the like), security (e.g., IPSec, SSL, and/or the like), and/or the like. 
     Data center architecture  100  further includes a database proxy  130 . In some embodiments, database proxy  130  is consistent with any of the database proxies of  FIGS. 1-6 and 9 . In some embodiments, database proxy  130  is a NoSQL proxy. As shown in  FIG. 10 , database proxy  130  includes several modules that may each individually and/or collectively be implemented using any suitable combination of hardware and/or software. In some embodiments, the components of database proxy  130  (as discussed in further detail below) may be implemented using any suitable combination of one or more central processing units, processors, multi-core processors, microprocessors, FPGAs, ASICs, SOCs, off the shelf components, boards, and/or the like; including, for example, a combination of one or more central processing units and FPGAs, a combination of one or more FPGAs and SOCs, and/or the like. As would be understood by one of ordinary skill, the one or more processors, multicore processors, microprocessors, and/or the like may be executing software stored in non-transitory machine-readable media (not shown). Some common forms of machine readable media that may include the processes and methods are, for example, floppy disk, flexible disk, hard disk, magnetic tape, any other magnetic medium, CD-ROM, any other optical medium, RAM, PROM, EPROM, FLASH-EPROM, any other memory chip or cartridge, and/or any other medium from which a processor or computer is adapted to read. 
     Database proxy  130  includes a request processor  131 , a cache  145 , a database plugin  150 , a logging and metric unit  159 , and several network interfaces  132 ,  139 , and  152 . Request processor  131  is responsible for the processing of database requests received through network interface  132  and/or network interface  139 . Request process  131  is further responsible for sending database requests to database plugin  150  when the database request involves underlying database action and for sending database requests to other database proxies when those other database proxies are responsible for processing one or more portions of the database request. Request processor  131  further uses cache  145  for local and/or other cache storage. In some examples, cache  145  may be a persistent cache that stores data in non-volatile storage such as Flash/SSD. 
     Similar to network interface  113 , network interface  132  may include a combination of software drivers, firmware, hardware modules, and/or the like that provide network access and network services as would be expected in a network driver provide support for layered network systems such as TCP/IP, OSI, and/or the like. In some examples, network interface  132  may include physical layer support, medium access control (e.g., Ethernet, and/or the like), access to routing services (e.g., IP), access to delivery services (e.g., TCP, UDP, and/or the like), support for network management (e.g., ICMP, ARP, DHCP, and/or the like), one or more packet processors, one or more queues, one or more application layer APIs (e.g., HTTP, other REST APIs, and/or the like), security (e.g., IPSec, SSL, and/or the like), and/or the like. Network interface  132  receives database requests from application  111  via client-side driver  112  and network  120 . As each of the database requests is received, it is assigned a request identifier by request processor  131  to aid in tracking the database requests as they are processed by database proxy  130 . In some examples, the identifier may correspond to a session identifier, connection identifier, and/or the like. 
     Request processor  131  includes an index converter  133 . As database requests are received from client  110  via client-side driver  112  and network  120 , the database requests are forwarded by network interface  132  to index converter  133 . Index converter  133  provides support for translation of secondary indices included as part of each of the database requests to primary indices that are used to organize and store the database records cached by request processor  131 . In some examples, the index converter  133  may operate at line rate so that the index conversion of the database read request does not slow down the pipeline of database requests being handled by request processor  131 . In some examples, index converter  133  may use one or more lookup and/or cross-reference structures, such as one or more tables, to convert the database requests that reference data using one or more of the secondary indices to database requests that rely on the primary indices. For example, when a database request specifies a subset of data (e.g., via a “WHERE” clause or similar) using columns or fields that correspond to one of the secondary indices, index converter  133  modifies the database request to use the primary indices. In some examples, this index conversion allows for the data request to be completed using the more efficient primary indices. When a database request specifies data using just primary keys, the database request is passed through index converter  133  without change. 
     After being processed by index converter  133 , the database requests are forwarded to a serdes engine  134 . In some examples, serdes engine  134  may support various serdes protocols (e.g., JSON, ProtoBuf, Thrift, and/or the like). In some examples, the serdes engine  134  may operate at line rate so that the data protocol conversion of the database read request does not slow down the pipeline of database requests being handled by request processor  131 . In some examples, serdes engine  134  is used to support conversion between the data formatting protocols used by application  111  to the data formatting protocols used by request processor  131 . This allows the other modules of request processor  131  to operate natively in their preferred data formatting protocol without having to perform separate conversion of the data formatting protocols of application  111 . For example, when a database request includes data in the JSON format and request processor  131  works natively in the BSON format, serdes engine  134  converts the JSON formatted data objects to BSON formatted data objects. When a database request includes data already in the native format of request processor  131 , the database request is passed through serdes engine  134  without change. 
     After being processed by index converter  133  and/or serdes engine  134 , the database requests are forwarded to a hashing unit  135 . Hashing unit  135  examines the primary index, range of primary indices, and/or set of primary indices included in a database request and applies a hashing function to each index to determine a fixed-length hash value for each index. In some examples, the hashing function may be any suitable hashing function, such as a cyclic redundancy check, a checksum, a universal hash, a non-crytographic hash, and/or the like. In some examples, the structure of the hashing function and how it hashes each of the indices is based on how request processor  131  organizes and/or retrieves data. In some examples, when request processor  131  organizes and/or retrieves data consistent with a columnar data format, such as the columnar data format of Apache Cassandra, the hashing function may be applied to a key space, a table identifier, and/or a key or primary index value from the database request. When the database request includes a range of primary indices and/or a group of primary indices, the hashing function may be applied multiple times to different index values to determine a series of hash values corresponding to the database request. In some examples, other database formats may be used with different hashing functions. The one or more hash values are then forwarded to a router  136  for further processing. 
     In some embodiments, router  136  corresponds to the proxy finite state machine, configuration and coordination engine, and/or the load balancer of  FIG. 9 . Router  136  determines the one or more locations where the data requested and/or identified by each database request is stored based on the one or more hash values provided by hashing unit  135  for the database request. Router  136  examines each of the hash values to determine whether the hash value falls within a range of hash values that are the responsibility of database proxy  130  or one of the other database proxies  171 - 179  forming a proxy cluster with database proxy  130 . In some examples, the set of possible hash values are divided into a plurality of hash value ranges with each of database proxy  130  and database proxies  171 - 179  being responsible for one or more of the hash value ranges. In some examples, the hash values may be mapped according to a consistent hashing and/or similar arrangement where the set of possible hash values are mapped to a circular space with each of database proxy  130  and database proxies  171 - 179  being assigned to one or more angular ranges within the circular space. In some examples, the division of hash values among database proxy  130  and the one or more other database proxies  171 - 179  supports load balancing among database proxy  130  and the one or more other database proxies  171 - 179 . 
     Router  136  then makes a determination, for each hash value, whether further processing of data associated with that hash value is to be performed by database proxy  130  or one of the other database proxies  171 - 179 . When the hash value corresponds to one of the ranges of hash values assigned to database proxy  130 , database proxy  130  accesses the data associated with the hash value. When the hash value corresponds to one of the ranges of hash values associated with a hash value of one or the other database proxies  171 - 179 , the processing of the data associated with the hash value is forwarded to a corresponding one of the other database proxies  171 - 179  that is assigned the hash value. The database request with the hash value is forwarded to the corresponding one of the other database proxies  171 - 179  using network interface  139 . When the corresponding one of the other database proxies  171 - 179  finishes processing of the forwarded database request, the other database proxy  171 - 179  returns results and/or a response to router  136  through network interface  139 . 
     Network interface  139  is similar to network interfaces  113  and/or  132  and provides interconnectivity with each of the other database proxies  171 - 179  via a network  160  that is similar to network  120 . In some examples, each of the other database proxies  171 - 179  may be substantially similar to database proxy  130  and may receive the forwarded database request on a corresponding network interface  139 . In some examples, network interface  139  may provide connection pooling with the corresponding network interfaces  139  in each of the other database proxies  171 - 179 . And although  FIG. 10  shows two other database proxies  171  and  179 , any number of other database proxies is possible including one, three, and/or four or more. 
     Referring back to router  136 . When router  136  determines that the hash value is assigned to database proxy  130 , router  136  examines the database request to determine whether it is a read, a write, an update, or a delete request. When the database request is a read request, router  136  uses a storage engine  140  to determine whether a local copy of the associated data is stored in cache  145 . In some examples, the hash value determined by hashing unit  135  may be used by storage engine  140  as an index into cache  145  and a determination is made whether the associated data is stored in cache  145  by looking up hash value in cache  145 . In some examples, when the hash value is not used as an index by cache  145 , storage engine  140  and/or cache  145  may compute a different hash and use that to determine whether the associated data is stored in cache  145 . When the associated data is stored in cache  145 , it is retrieved from cache  145  by storage engine  140  and returned to router  136  as results for the database request. In some examples, storage engine  140  and/or cache  145  may use any suitable data replacement policy, such as least-recently use, least-frequently used, and/or the like. In some embodiments, storage engine  140  includes an H-MMU, which is further described in U.S. Pat. No. 9,286,221, which is hereby incorporated by reference in its entirety. In some embodiments, storage engine  140  overlays one or more higher-order data models onto cache  145  that provide support for various NoSQL database types. In some examples, the one or more higher-order models may include columnar (such as used by Apache Cassandra), graph, document store, and/or other suitable data formats. 
     When the database request is a write request, the hash value (or other index used by storage engine  140  and/or cache  145 ) is used to store the results in cache  145  and then a copy is written to an underlying database using a database plugin  150 . When the database request is a delete request, the hash value (or other index used by storage engine  140  and/or cache  145 ) is used to delete the corresponding data from cache  145  if a copy is stored in cache  145  and database plugin  150  is used to delete the corresponding data from the underlying database. When the database request is an update request, the hash value (or other index used by storage engine  140  and/or cache  145 ) is used to update the corresponding data in cache  145  if the corresponding data is already stored in cache  145  or to store the corresponding data in cache  145  if the corresponding data in not already stored in cache  145 . A copy is then written to the underlying database using database plugin  150 . In some examples, a write, update, and/or a delete request is forwarded to the underlying database by database plugin  150  consistent with the writing policy of the underlying database, whether that is a write-back and/or a write-through policy. 
     When a database request is associated with multiple hash values, router  136  subdivides the database request into a series of database sub-requests corresponding to each of the hash values. Each of the sub-requests and associated hash values is then processed separately by router  136  using storage engine  140 , cache  145 , database plugin  150 , and/or one of the other database proxies  171 - 179 . Router  136  then collects the sub-results and/or sub-responses associated with each of the hash values into composite results and/or a composite response. In some examples, tracking of the various sub-requests and sub-results may be managed by tagging each of the sub-requests and sub-results with the request identifier assigned to the originating database request when it was received by request processor  131 . 
     After the results and/or response to the database query is assembled by router  136 , the results and/or response are forwarded to a compute block  137 . Compute block  137  provides support for regular expression evaluation, filtering, and/or the like that may be included as part of the database request. In some examples, compute block  137  may provide support for compression, encryption, and/or similar functions. In some examples, compute block  137  supports libraries capable of extending a language framework such as node.js, via support of stored procedures, and/or the like. In some examples, compute block  137  may be implemented via a compilation of a domain-specific language, such as Ragel and/or the like, which may be used to support descriptions of complex data filtering and classing using regular expressions, that will generate C code for operation on the one or more processors or that can alternatively be compiled into an FPGA using a high-level synthesis compiler. When the results and/or response are not subject to expression, filtering, and/or the like as part of the database request, the results and/or response are passed through compute block  137  without change. 
     The results and/or response are then forwarded to a serdes engine  138  in further preparation for returning the results and/or response to requesting application  111 . In some examples, serdes engine  138  is similar to serdes engine  134  and is responsible for converting data objects from the data formatting protocol used by request processor  131  to the data formatting protocol used by application  111 . When application  111  and request processor  131  use the same data formatting protocols and/or the results and/or response do not include any data objects, the results and/or response are passed through serdes engine  138  without change. 
     After processing by serdes engine  138 , the results and/or response are passed back to application  111  by network interface  132 . In some examples, correct delivery of the results and/or response to application  111  is managed using the request identifier assigned to the originating database request when it was received by database proxy  130 . 
     Database plugin  150  is selected from a series of possible database plugins depending upon the type of the underlying database as each underlying database typically uses different query languages, data formatting protocols, writing policies (write-back and/or write-through), transaction policies, underlying architectures, and/or the like. In some examples, the types of underlying database supported by database plugin  150  may include Apache Cassandra, Mongo, Hbase, Hadoop, and/or the like. Database plugin  150  includes a serdes engine  151  that is similar to serdes engine  134  and/or serdes engine  138 . Serdes engine  151  is responsible for converting data objects from the data formatting protocol used by database proxy  130  to the data formatting protocol used by the underlying database. When the underlying database and request processor  131  use the same data formatting protocols and/or the database request does not include any data objects, the database request is passed through serdes engine  151  without change. 
     After processing by serdes engine  151 , the database request is forwarded to network interface  152  for delivery to a database server  190  for the underlying database. Database server  190  provides access to one or more databases  191 - 199  that form the underlying database. Network interface  152  is similar to network interfaces  113 ,  132 , and/or  139  and provides interconnectivity with database server  190  via a network  180  that is similar to network  120  and/or  160 . In some examples, network interface  152  and database plugin  150  may access database server  190  using one or more APIs of database server  190 . In some examples, network interface  152  may provide connection pooling with a network interface (not shown) in database server  190 . And although  FIG. 10  shows a single database server, database plugin  150  is capable of communicating with two or more database servers. 
     After database server  190  returns a response to the database request (either as results of a read or status of a write, update, or delete) to database plugin  150  via network interface  152 , the results and/or response are forwarded to a serdes engine  153  that is similar to serdes engine  134 ,  138 , and/or  151 . Serdes engine  153  is responsible for converting data objects from the data formatting protocol used by the underlying database to the data formatting protocol used by database proxy  130 . When the underlying database and database proxy  130  use the same data formatting protocols and/or the results and/or response do not include any data objects, the results and/or response are passed through serdes engine  153  without change. 
     After processing by database plugin  150 , the results and/or response are returned to router  136  where they may be combined with other results and/or responses for return to application  111  as described above. When the results are in response to a database read request, the results may be stored in cache  145  as previously discussed. 
     Logging and metric unit  159  provides logging and analytics support for database proxy  130 . In some examples, logging and metric unit  159  provides one or more logs supporting by one or logging APIs that the other units of database proxy  130  (e.g., request processor  131 , network interface  132 , index converter  133 , serdes engine  134 , hashing unit  135 , router  136 , compute block  137 , serdes engine  138 , network interface  139 , storage engine  140 , cache  145 , serdes engine  151 , network interface  152 , and/or serdes engine  153 ) may use to log their respective activities as they handle database requests. In some examples, the one or more logs may be used to track database requests, debug the processing of requests, and/or the like. In some examples, the one or more logs may be accessed by clients (such as client  110  and/or application  111 ) and/or administrators to monitor the activities of database proxy  130 . In some examples, logging and metric unit  159  may provide one or more analytics engines that may determine one or more performance metrics (e.g., throughput, latency, utilization, cache capacity, hit rates, and/or the like) and/or one or more operational statistics. In some examples, the one or more performance metrics and/or the one or more operational statistics may be accessed by clients (such as client  110  and/or application  111 ) and/or administrators via one or more APIs. In some examples, one or more of the entries in the one or more logs, the one or more performance metrics, and/or the one or more operational statistics may be accessed and/or shared using network interface  132 . 
     As discussed above and further emphasized here,  FIG. 10  is merely an example which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. In some embodiments, database proxy  130  may further include more than one database plugin to support the forwarding of database requests to multiple database servers, to support database servers of different types, and/or the like. 
     In some embodiments, different interconnections are possible between client  110 , database proxy  130 , the other database proxies  171 - 179 , and/or database server  190 . In some examples, any two or more of network interface  132 , network interface  139 , and/or network interface  180  may be combined so that the same hardware and/or software modules may be usable by database proxy  130  to communicate with client  110 , the other database proxies  171 - 179 , and/or database server  190 . In some examples, the decision whether to use separate or combined network interfaces may be based on balancing between the extra throughput of parallelism versus fewer circuits and/or modules within database proxy  130 . In some examples, whether to use separate or combined network interfaces may depend on the number of network ports, buffer sizes, and/or the like supported by network interfaces  132 ,  139 , and/or  152 . Similarly, any two or more of network  120 ,  160 , and/or  180  may be a same network. 
     In some embodiments, one or more of the interconnections between database proxy  130  and client  110 , the other database proxies  171 - 179 , and/or database server  190  may be implemented using local port connections, buses, and/or the like rather than network connections. In some examples, when database proxy  130  is installed in client  110  (such as in the embodiments of  FIG. 5 ), database proxy  130  may be interconnected to the rest of client  110  using one or more ports, one or more buses, and/or the like. In some examples, database proxy  130  and/or one or more of the other database proxies  171 - 179  may be optionally mounted in a same chassis allowing interconnect between database proxy  130  and the one or more of the other database proxies  171 - 179  through a mid-plane and/or back-plane connection mechanism. In some examples, when database proxy  130  is installed in database server  190  (such as in the embodiments of  FIGS. 3, 4 , and/or  6 ), database proxy  130  may be interconnected to the rest of database server  190  using one or more ports, one or more buses, and/or the like. In some embodiments, the one or more ports and/or one or more buses may be PCIe buses, QuickPath Interconnects, accelerator coherence ports, advanced microcontroller bus architecture (AMB A) buses, and/or the like. 
       FIG. 11  is a simplified diagram of a method  200  of handling read requests using database proxies according to some embodiments. One or more of the processes  202 - 240  of method  200  may be implemented, at least in part, in the form of executable code stored on non-transient, tangible, machine readable media that when run by one or more processors (e.g., one or more processors of database proxy  130 ) may cause the one or more processors to perform one or more of the processes  202 - 240 . In some embodiments, one or more of the processes  202 - 240  of method  200  may be implemented, at least in part, using one or more hardware modules including one or more ASICs, one or more FPGAs, and/or the like. In some embodiments, method  200  is usable to receive and process database read requests sent to a database proxy, such as database proxy  130  and/or any of the other database proxies  171 - 179 , from an application, such as application  111 . The ordering of processes  202 - 240  in  FIG. 11  is exemplary only and other possible orderings and/or arrangements of processes  202 - 240  are possible. In some examples, one or more of processes  202 - 240  may be performed concurrently. In some embodiments, processes  208 - 214 ,  218 - 232 ,  236 , and/or  238  may be performed multiple times when a database request involves data associated with multiple hash values. In some embodiments, one or more of processes  204 ,  206 ,  222 ,  228 ,  236 , and/or  238  may be optional and can be omitted. In some embodiments, other processes not shown in  FIG. 11  may also be part of method  200 . In some embodiments, method  200  is consistent with the method and processes of  FIG. 8 . 
     At a process,  202  a database read request is received from an application. In some examples, the database read request may be received by a database proxy, such as database proxy  130 , from an application, such as application  111 , via an interface, such as network interface  132 . The database read request may be in the form of a query in a standard query language, such as Cassandra query language and/or the like, and may include a request for one or more entries and/or fields stored in the database being supported by the database proxy. In some examples, the database read request may be received using one or more API calls invoked by the application and/or a client-side driver, such as client-side driver  112 , used to access the database through the database proxy. In some examples, the database read request may be assigned a request identifier, such as a session identifier, connection identifier, and/or the like so that the database read request may be tracked throughout method  200 . 
     At an optional process  204 , any secondary indices used in the database read request are converted to primary indices by an index converter, such as index converter  133 . In some examples, the index conversion may include using one or more lookup and/or cross-reference structures, such as one or more tables, to convert the secondary indices in the database read request received during process  202  to primary indices. In some examples, the index conversion may occur at line rate so as not to slow down the pipeline of database requests being handled by the database proxy. When the database read request specifies data using just primary keys, process  204  may be omitted. 
     At an optional process  206 , data objects in the database read request that are not in data formatting protocols used by the database proxy are converted to data formatting protocols used by the database proxy using a serdes engine, such as serdes engine  134 . In some examples, the format conversion may occur at line rate so as not to slow down the pipeline of database requests being handled by the database proxy. When the database read request does not include data objects in a data formatting protocol that are not natively supported by the database proxy, process  206  may be omitted. 
     At a process  208 , the database entries referenced by the database read request are hashed by a hashing unit, such as hashing unit  135 . The hashing unit examines the primary index, range of primary indices, and/or set of primary indices included in the database read request and applies a hashing function to each index to determine a fixed-length hash value for each index. When the database request includes a range of primary indices and/or a group of primary indices, the hashing function may be applied multiple times to difference index values to determine a series of hash values corresponding to the database read request. Each of the hash values determined during process  208  is then passed on to the other processes of method  200  for further handling as a separate database read request (i.e., a sub-request). 
     At a process  210 , it is determined whether the hash value corresponds to a hash value assigned to the database proxy (i.e., locally) or to another database proxy (peer proxy) in the system. In some examples, the hash value may be compared to one or more ranges of hash values assigned to the local database proxy to determine whether the local database proxy is going to handle the database read associated with the hash value or whether the database read request is to be forwarded to one of the peer database proxies for handling. In some examples, when the hash value is assigned to one of the peer database proxies, the peer database proxy is identified based on the one or more ranges of hash values assigned to that peer database proxy. When the hash value is assigned to the local database proxy, the portion of the database read request corresponding to the hash value is forwarded to process  218  for further handling. When the hash value is assigned to one of the peer database proxies, the portion of the database read request corresponding to the hash value is forwarded to process  212  for further handling. 
     At the process  212 , the portion of the database read request corresponding to the hash value is sent to the appropriate peer database proxy. In some examples, the portion of the database read request corresponding to the hash value may be forwarded to the peer database proxy via an interface, such as network interface  139 . In some examples, to aid in tracking the database read request, the request identifier may be sent along with the portion of the database read request sent to the peer database proxy and/or associated with the connection used to send the portion of the database read request to the peer database proxy. In some examples, use of the request identifier allows for the portion of the database read request to be sent and the results received without the sending and/or receiving having to occur in a strict order. 
     At a process  214 , when the peer database proxy completes processing of the portion of the database read request (e.g., to retrieve the data requested by the portion of the database read request), the results are returned from the peer database proxy to the local database proxy. In some examples, the request identifier included in the received results and/or associated with the connection to the peer database proxy may be used to associate the results with the database read request received during process  202  and without having to receive the results in any strict order. Once the results are received they are further processed beginning with a process  236 . 
     As an alternative to processes  202 - 214 , at a process  216 , the database read request is received from a peer database proxy. In some examples, the database read request may be received from the peer database proxy as a counterpart to a corresponding send process, such as process  212 , in the peer database proxy. Because the database read request has been partially processed by the peer database proxy and the corresponding hash value has been determined to belong to the local database proxy, the database read request may be handled without having to use processes  202 - 210 . In some examples, the database read request may be assigned a request identifier. Once received, the database read request is passed to process  218  for further handling. 
     At the process  218 , it is determined whether the data corresponding to the hash value has been previously retrieved and is stored in a local cache, such as cache  145 . When the data corresponding to the hash value is stored in the local cache (i.e., a hit occurs), the database read request is passed to the process  220  for further processing. When the data corresponding to the hash value is not stored in the local cache (i.e., a miss occurs), the database read request is passed to a database plugin, such as database plugin  150 , for further processing beginning with a process  222 . 
     At the process  220 , the data corresponding to the hash value is retrieved from the cache using a storage engine, such as storage engine  140 . The retrieved data is then passed to a process  232  for further handling. 
     At the optional process  222 , data objects in the database read request that are not in data formatting protocols used by the underlying database are converted to data formatting protocols used by the underlying database using a serdes engine, such as serdes engine  151 . In some examples, the format conversion may occur at line rate so as not to slow down the pipeline of database requests being handled by the database proxy and/or the database plugin. When the database read request does not include data objects in a data formatting protocol that are not supported by the underlying database, process  222  may be omitted. 
     At a process  224 , the database read request is sent to a database server associated with the underlying database, such as database server  190 , for further handling. In some examples, the database read request corresponding to the hash value may be forwarded to the database server via an interface, such as network interface  152 . In some examples, to aid in tracking the database read request, the request identifier may be sent along with the database read request sent to the database server and/or associated with the connection used to send the database read request to the database server. In some examples, use of the request identifier allows for the database read request to be sent and the results received without the sending and/or receiving having to occur in a strict order. 
     At a process  226 , when the database server completes processing of the database read request (e.g., to retrieve the data requested by the database read request from the underlying database), the results are returned from the database server to the database plugin. In some examples, the request identifier included in the received results and/or associated with the connection to the database server may be used to associate the results with the database read request received during process  202  and without having to receive the results in any strict order. 
     At an optional process  228 , data objects in the results from the database server that are not in data formatting protocols used by the database proxy are converted to data formatting protocols used by the database proxy using a serdes engine, such as serdes engine  153 . In some examples, the format conversion may occur at line rate so as not to slow down the pipeline of database requests being handled by the database proxy and/or the database plugin. When the results do not include data objects in a data formatting protocol that are not natively supported by the database proxy, process  228  may be omitted. 
     At a process  230 , the results from the database server are stored in the cache. This allows subsequent requests for the data corresponding to the results to be more quickly retrieved using process  220  as a cache hit in a subsequent request for the same data. In some examples, when there is no space in the cache to store the results, one or more values in the cache may be replaced using any suitable cache replacement policy, such as least-recently used, least-frequently used, and/or the like. After the results are stored in the cache, the results are further processed using process  232 . 
     At the process  232 , the original source of the database read request is determined as that determines to where the results are to be sent. When the database read request came from a peer database proxy via process  216 , the results are returned to the peer database proxy using a process  234 . When the database read request came from an application via process  201 , the results are returned to the application beginning with a process  236 . However, in some embodiments, when the hashing of process  208  resulted in splitting the database read request into multiple sub-requests, the results of each of the sub-requests may be gathered and/or combined into a single set of results to be returned to the application beginning with process  236 . 
     At the process  234 , the results are returned to the peer database proxy that sent the database read request during process  216 . In some examples, the request identifier assigned to the database read request during process  216  may be used to return the results to the correct peer database proxy. In some examples, the database read request may be returned to a corresponding process  214  of the peer database proxy. Once the results are returned to the peer database proxy, processing of the database read request is complete. 
     At the optional process  236 , the results of the database read request are processed using a compute block, such as compute block  137 . In some examples, the compute block may apply any regular expression, filter, compression, encryption, stored procedure, and/or the like specified in the database read request to the results of the database read request. When the results are not subject to computation as part of the database read request, process  236  may be omitted. 
     At an optional process  238 , data objects in the results that are not in data formatting protocols used by the application are converted to data formatting protocols used by the application using a serdes engine, such as serdes engine  138 . In some examples, the format conversion may occur at line rate so as not to slow down the pipeline of database requests being handled by the database proxy. When the results do not include data objects in a data formatting protocol that are not supported by the application, process  238  may be omitted. 
     At a process  240 , the results are returned to the application using the interface used to receive the database read request during process  202 . In some examples, the request identifier assigned to the database read request during process  202  may be used to return the results using the same connection on which the database read request was received. In this way, the results may be returned to the appropriate place in the application. Once the results are returned to the application, processing of the database read request is complete. 
       FIG. 12  is a simplified diagram of a method  300  of handling update, write, or delete requests using database proxies according to some embodiments. One or more of the processes  302 ,  204 - 214 ,  304 ,  222 - 228 ,  306 ,  232 ,  234 , and  240  of method  300  may be implemented, at least in part, in the form of executable code stored on non-transient, tangible, machine readable media that when run by one or more processors (e.g., one or more processors of database proxy  130 ) may cause the one or more processors to perform one or more of the processes  302 ,  204 - 214 ,  304 ,  222 - 228 ,  306 ,  232 ,  234 , and  240 . In some embodiments, one or more of the processes  302 ,  204 - 214 ,  304 ,  222 - 228 ,  306 ,  232 ,  234 , and  240  of method  300  may be implemented, at least in part, using one or more hardware modules including one or more ASICs, one or more FPGAs, and/or the like. In some embodiments, method  300  is usable to receive and process database write, update, and delete, requests sent to a database proxy, such as database proxy  130  and/or any of the other database proxies  171 - 179 , from an application, such as application  111 . The ordering of processes  302 ,  204 - 214 ,  304 ,  222 - 228 ,  306 ,  232 ,  234 , and  240  in  FIG. 12  is exemplary only and other possible orderings and/or arrangements of processes  302 ,  204 - 214 ,  304 ,  222 - 228 ,  306 ,  232 ,  234 , and  240  are possible. In some examples, process  306  may be performed before and/or concurrently with processes  222 - 228 . In some examples, one or more of processes  302 ,  204 - 214 ,  304 ,  222 - 228 ,  306 ,  232 ,  234 , and  240  may be performed concurrently. In some embodiments, processes  210 - 214 ,  304 ,  222 - 228 ,  306 ,  232 ,  234 , and/or  240  may be performed multiple times when a database request involves data associated with multiple hash values. In some embodiments, one or more of processes  204 ,  206 ,  222 , and/or  228  may be optional and can be omitted. In some embodiments, other processes not shown in  FIG. 12  may also be part of method  300 . In some embodiments, method  300  is consistent with the method and processes of  FIG. 8 . 
     At a process,  302  a database write, update, or delete request is received from an application. In some examples, the database write, update, or delete request may be received by a database proxy, such as database proxy  130 , from an application, such as application  111 , via an interface, such as network interface  132  using a process similar to process  202 . The database write, update, or delete request may be in the form of a query in a standard query language, such as Cassandra query language and/or the like, and may include a write, update, or delete request for one or more entries and/or fields stored in the database being supported by the database proxy. In some examples, the database write, update, or delete request may be received using mechanisms and/or processes similar to those discussed with respect to process  202 . In some examples, the database write, update, or delete request may be assigned a request identifier, such as a session identifier, connection identifier, and/or the like so that the database write, update, or delete request may be tracked throughout method  300 . 
     The database write, update, or delete request is then processed using processes  204 - 208  in much the same fashion as database read requests are handled by the corresponding processes in method  200 . At the process  210 , each of the hash values determined during process  208  is examined to determine whether the hash value is assigned to one of the one or more ranges of hash values assigned to the local database proxy. When the hash value is assigned to the local database proxy, the database write, update, or delete request is passed to process  222  for further handling. When the hash value is assigned to a peer database proxy, the database write, update, or delete request is sent to the peer database proxy for handling using processes  212  and  214  in much the same way as database read requests are handled by processes  212  and  214  in method  200 . 
     As an alternative to processes  302  and  204 - 214 , at a process  304 , the database write, update, or delete request is received from a peer database proxy. In some examples, the database write, update, or delete request may be received from the peer database proxy as a counterpart to a corresponding send process, such as process  212 , in the peer database proxy in much the same way database read requests are received during process  216  of method  200 . In some examples, the database write, update, or delete request may be assigned a request identifier. Once received, the database write, update, or delete request is passed to process  222  for further handling. 
     The database write, update, or delete request is then processed using processes  222 - 228  in much the same fashion as database read requests are handled by the corresponding processes in method  200 . This allows the database write, update, or delete request to be reflected in the data stored in the underlying database. In some examples, the database write, update, or delete request may be processed according to the write polity (e.g., write-through or write-back) of the database plugin and/or the underlying database. 
     At a process  306 , the database write, update, or delete request is applied to the cache. This allows subsequent requests for the data corresponding to the database write, update, or delete request to be more quickly retrieved using process  220  as a cache hit in a subsequent request for the same data using method  200 . When the database request is a write request, the hash value (or other index used by the cache) is used to store the data specified by the database write request in the cache. When the database request is a delete request, the hash value (or other index used by the cache) is used to delete the corresponding data from the cache if a copy is stored in the cache. When the database request is an update request, the hash value (or other index used by the cache) is used to update the corresponding data in the cache if the corresponding data is already stored in the cache or to store the corresponding data in the cache if the corresponding data in not already stored in the cache. In some examples, when there is no space in the cache to store the update, one or more values in the cache may be replaced using any suitable cache replacement policy, such as least-recently used, least-frequently used, and/or the like. 
     After the database write, update, or delete request is used to update the cache during process  306 , the response from the database write, update, or delete request is further processed using processes  232 ,  234 , and  240  in much the same manner as the same processes in method  200 . In some examples, because database write, update, and/or delete requests do not typically return results, a response (typically in the form of success or failure) is returned to the peer database proxy or application as appropriate. Once the response is returned by process  234  or  240 , processing of the database write, update, or delete request is complete. 
     As described above, the various embodiments of the database and NoSQL proxies and the data center architectures using database and NoSQL proxies are advantageously able to achieve high throughput, access large amounts of data using tiered memory, and/or accelerate serialization and deserialization operations. 
     Some examples of the proxies and servers described herein may include non-transient, tangible, machine readable media that include executable code that when run by one or more processors may cause the one or more processors to perform the processes and methods described herein. Some common forms of machine readable media that may include the processes and methods are, for example, floppy disk, flexible disk, hard disk, magnetic tape, any other magnetic medium, CD-ROM, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, RAM, PROM, EPROM, FLASH-EPROM, any other memory chip or cartridge, and/or any other medium from which a processor or computer is adapted to read. 
     Although illustrative embodiments have been shown and described, a wide range of modification, change and substitution is contemplated in the foregoing disclosure and in some instances, some features of the embodiments may be employed without a corresponding use of other features. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. Thus, the scope of the invention should be limited only by the following claims, and it is appropriate that the claims be construed broadly and in a manner consistent with the scope of the embodiments disclosed herein.