When Shouldn't You Use Redis?
Tags: redis, database, discuss, beginners
Published: 2024-05-28 17:58:00

Well we can say that - 
> Redis: Where your data goes to wait for someone to remember it exists. 💀

![image](https://media.giphy.com/media/v1.Y2lkPTc5MGI3NjExdGFhNGZ4MXljcnZ4bGl2bTcwYm1hNzRqbGNyMGJyaTB4bm10cXYwYyZlcD12MV9pbnRlcm5hbF9naWZfYnlfaWQmY3Q9Zw/pjPfdL0lAmhuwcuM59/giphy.gif)

Or an extra layer of database to make your application fast.

This is not enough to learn and understand the use cases of Redis.

Redis offers a versatile toolkit for various application functionalities. Let's explore some key use cases, their architectural considerations, advantages, alternatives, and limitations:

**1. Session Store**

- **Architecture**: You can deploy Redis as a single instance for smaller applications. For scalability, consider using Redis Cluster, which distributes data across multiple nodes.

- **Advantages**: Redis excels at storing session data due to its blazing-fast speed. This allows web applications to manage user sessions efficiently and personalize experiences quickly. Additionally, Redis Cluster facilitates easy horizontal scaling as your application grows.

- **Alternatives**: Memcached is a simpler alternative, but it offers fewer features compared to Redis.

- **Limitations**: While Redis offers persistence options to mitigate data loss on server failure, it's crucial to consider this potential limitation.


**2. Caching**

- **Architecture**: Similar to session storage, a single Redis instance or a Redis Cluster can be employed for caching.

- **Advantages**: By caching frequently accessed data from your main database in Redis, you can significantly boost application performance. Since Redis retrieves data much faster than a traditional database, the overall responsiveness of your application improves. Furthermore, caching reduces the load on your main database, improving its overall efficiency.

- **Alternatives**: In-memory caching libraries can be integrated within your application code. However, these libraries typically offer less functionality compared to a dedicated caching solution like Redis.

- **Limitations**: The primary limitation of caching with Redis is the data size constraint due to its in-memory storage.


**3. Message Queues**

- **Architecture**: Redis can function as a message queue using a single instance or a Redis Cluster.

- **Advantages**: Leveraging Redis as a message queue enables asynchronous task processing within your application. This improves scalability and fault tolerance by decoupling different parts of your application. Tasks can be processed independently, improving overall performance.

- **Alternatives**: RabbitMQ and Apache Kafka are more complex message queueing systems that offer features like persistence, which might be beneficial for high-throughput workloads.

- **Limitations**: While Redis is a capable message queue, it might not be suitable for very large message sizes or require complex features for extremely high-volume message processing.


**4. Real-time Applications**

- **Architecture**: To build real-time applications with Redis, you can utilize a single instance or a Redis Cluster configured with Pub/Sub messaging. Pub/Sub allows real-time data broadcasting to multiple clients simultaneously.

- **Advantages**: The low-latency data broadcasting capabilities of Redis Pub/Sub are ideal for building features like live chat or social media feeds. This enables real-time updates and interactions within your application.

- **Alternatives**: WebSockets and Server-Sent Events are alternative approaches for real-time functionality, but they can be more complex to implement.

- **Limitations**: The number of concurrent subscribers that Redis Pub/Sub can handle might be limited for very high-traffic applications.


**5. Leaderboards**

- **Architecture**: A single instance or a Redis Cluster can be used for leaderboards, leveraging Redis Sorted Sets. Sorted Sets provide efficient storage and retrieval of ranked data.

- **Advantages**: Maintaining leaderboards becomes effortless with Redis Sorted Sets. They allow for efficient storage, retrieval, and updates of ranked data, making it easy to keep leaderboards current.

- **Alternatives**: Relational databases can be used for leaderboards, but they might require complex queries and offer less performance compared to Redis Sorted Sets.

- **Limitations**: While Redis excels at basic leaderboards, it might lack functionalities for highly complex leaderboard logic requiring additional features beyond its core capabilities.

Well, let's look at some of the use cases where we should not consider Redis.

While Redis is a powerful tool, there are situations where it might not be the ideal choice. Here are 5 worst-case scenarios to consider when evaluating if Redis is the right fit for your needs:

- **Large Datasets**:  Redis is an in-memory data store.  If your data volume is massive and exceeds what can be comfortably stored in memory, Redis becomes impractical.  The cost of maintaining enough RAM to hold the entire dataset can be prohibitive. In such cases, traditional databases or distributed file systems like HDFS are better suited for handling large data volumes.

- **Durability Requirements**:  While Redis offers persistence options like snapshots and AOF (Append-only File), it's not designed for situations where absolute data consistency and zero downtime are paramount. Frequent data updates and the potential for data loss during failures make Redis less suitable for scenarios requiring the highest level of data durability. Relational databases with strong ACID (Atomicity, Consistency, Isolation, Durability) guarantees might be a better choice.

- **Complex Data Relationships**:  Redis excels at storing simple key-value pairs, sorted sets, and lists.  However, it's not ideal for modeling complex data relationships often found in relational databases.  If your application heavily relies on JOINs, complex queries involving multiple data entities, or intricate data schemas, a traditional relational database would be a more appropriate choice.

- **High-Throughput Writes**:  While Redis can handle a significant write volume, it might not be the best fit for scenarios with an extremely high number of writes per second. The in-memory nature of Redis can become a bottleneck for write-heavy workloads. Alternative solutions like Apache Kafka, designed specifically for high-throughput messaging, might be better suited for such use cases.

- **Limited Geographical Distribution**:  If your application requires low-latency data access across geographically distributed regions, Redis might not be the optimal solution. Setting up and managing multiple Redis clusters in different locations can be complex. Database solutions with built-in geographic replication or cloud-based offerings with global reach might be a better fit for geographically distributed deployments.

_Do share your thoughts about this article, and queries related to Redis in the comments._