Introduction to Redis

Redis (Remote Dictionary Server) is a fast database used for caching web pages to reduce server load, and message brokering to manage communication between systems.

Uses of Redis are:

• Caching frequently accessed data to improve website.
• Session storage for web applications
• Real-time analytics and leader boards.
• Managing queues or task lists in background job systems.

How Redis Work?

Redis acts as a caching layer between the database and the client to speed up data access and reduce the load on the main database. When a client asks for data, the API Gateway forwards the request to Redis.

If Redis has the data (cache hit), it returns it quickly through the API Gateway to the client. If the data is missing (cache miss), Redis retrieves it from the database, stores it in the cache for future requests, and then passes it back through the API Gateway to the client. This flow speeds up response times and reduces the database load.

Before starting to learn Redis we need to install redis on our system.

Now let's understand this with the help of example:

import redis
r = redis.Redis(host='localhost', port=6379, db=0)

r.set('name', 'Alia')
print(r.get('name').decode('utf-8'))  

r.set('name', 'Riya')
print(r.get('name').decode('utf-8')) 

r.delete('name')
print(r.get('name'))  

Output

Understand the above example:

import redis

This line imports the redis Python library, which allows you to talk to a Redis server from your Python code.

r = redis.Redis(host='localhost', port=6379, db=0)

Here, you are creating a Redis connection:

• host='localhost': connects to Redis running on your own computer
• port=6379: the default port Redis listens on
• db=0: Redis supports multiple logical databases numbered from 0, and you’re using database 0

So this "r" variable is now your handle to talk to Redis.

r.set('name', 'Alia')

This line stores the key name with the value Alia in Redis.

print(r.get('name').decode('utf-8'))

This retrieves the value stored under the key name (which is Alia) from Redis.

• r.get('name') returns the value in bytes format, e.g. b'Alia'
• .decode('utf-8') converts those bytes to a normal string, so it prints Alia.

Note: In this example, Redis is integrated with Python but redis can also be implemented in other programming languages like Java, JavaScript (Node.js), Go, Ruby, C# (.NET), PHP, and many more, using their respective Redis client libraries.

When to Use Redis Server?

Consider you have a MySQL database and you are constantly querying the database which reads the data from the secondary storage, computes the result, and returns the result.

If the data in the database is not changing much you can just store the results of the query in redis-server and then instead of querying the database which is going to take 100-1000 milliseconds, you can just check whether the result of the query is already available in redis or not and return it result which is going to be much faster as it is already available in the memory.

Note: In a messaging app, Redis can be used to store the last five messages that the user has sent and received using the built-list data structure provided in Redis.

Why Redis is so Fast?

Redis is fast because it keeps all its data in memory instead of on disk, so it doesn’t waste time reading from a hard drive. It also uses just one thread with an event loop to process commands, which avoids the complexity and delays of managing multiple threads.

On top of that, Redis uses well-optimized data structures and a simple, lightweight communication protocol called RESP to talk over the network. These design choices mean Redis can handle many requests at once, with very little delay, and respond almost instantly.

Read more here: Why Redis is so fast and popular?

Difference Between Redis Vs MongoDB

Both Redis and MongoDB are widely used databases, but there are some key differences between them that you should know:

Note: Redis is much faster than MongoDB, especially for tasks that rely on simple, high-throughput operations. The exact margin can vary, but for basic operations, Redis is often 10x to 100x faster than MongoDB.

Conclusion

Redis is a fast, in-memory data store ideal for caching, real-time analytics, and messaging. It offers high performance, scalability, and optional persistence, making it perfect for microservices and high-speed applications. Redis outperforms MongoDB in speed, especially for low-latency tasks.