# Centralized vs. Decentralized: Performance Comparison between BigchainDB and Amazon QLDB
## 1 Introduction  
Recently, ledger technology (LT) has become the focus point for industry, academia and research due to its potential to change the way in which things are organized and the way collaboration takes place within various domains such as supply chain, finance, healthcare, energy, telecommunications, etc. The concept of a blockchain-backed ledger brings verifiability into domains where data immutability is paramount, and where the necessity to ensure data integrity (and subsequently identify tampering) is the core feature in various processes. In this field, the cryptographical approach is new and has enabled the implementation of various technologies, culminating in the emergence of ledger technology. Classification can now be based on the type of entities that can modify the ledger (only by adding data), the checking of the ledger being done by any entity that tries to do so. In this regard, the ledger technology is classified as either centralized ledger technology (CLT) or decentralized ledger technology (DLT). In the first case, the data is transferred viaa central node. This node has control over the entire ledger system, as it is the only node capable of adding the data to the ledger. The ledger must be stored in a central repository and, if necessary, access to it can be severely restricted. In contrast, a decentralized ledger will have numerous nodes that are able to control and update the ledger's data, creating a network of centralized ledgers. At each data update, all nodes will receive a new copy of the ledger, allowing them to remain in sync. Actualization will only be allowed if a majority (or all) of the nodes validate the transaction. Most nodes will be unable to alter the data (just as in a centralized ledger network). As a result of the many advantages offered by these technologies, the number of companies interested in developing LT-based applications has increased in recent years. At present, there are many different LT-based databases on the market that can be used for this purpose. This fact raises several challenges in selecting the most suitable database for the desired application. Not all databases provide the same features or the specific characteristics required for a particular case. In order to assist developers in selecting the most appropriate database for a particular application, this paper presents the results of a comparative analysis of two LT-based databases (i.e., BigchainDB [1] and Amazon Quantum Ledger Database--QLDB [2]), by highlighting the advantages and disadvantages of each of these solutions. These databases have been chosen based on the fact that they have proven to be popular solutions for LT-based applications [3]. In this regard, these two databases were used by the authors to implement a traceability platform, called Smart Tracking Platform (STP) [4]. The platform's capabilities require a mechanism to verify the status of tracked products across various physical locations, as well as status changes, in a decentralized manner. The requirements of the proposed traceability platform are best addressed by a system that is fast enough to provide traceability and auditing capabilities. A ledger-based approach seems to provide the best results in this regard. The objectives for evaluating the candidate solutions were to ensure some basic features and low overhead. Although more functionality is usually desired (even if only for future expansion capabilities), only these minimum requirements were considered in our experiment. This paper is organized as follows. First, a literature review was conducted to evaluate the level of interest in the LT-based technologies and their impact on the market. Next, an overview of the ledger-based technologies was considered in order to analyze the opportunity for the utilization of the technology and the difficulties that can be unmasked in the implementation of solutions.