Question: Is Redis single-threaded?

Answer

Redis achieves high performance through its memory-centric design and optimization techniques like pipelining, batched writes, and LRU eviction. Although Redis is single-threaded, it can be scaled horizontally with sharding techniques and supports Lua scripting for complex atomic operations.

Redis employs asynchronous I/O to handle multiple connections simultaneously, allowing clients to send multiple commands without waiting for a response after each command, resulting in efficient execution of multiple commands in a single round-trip to the server.

Here's an example of how Redis handles multiple connections simultaneously using asynchronous I/O:

import redis

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

# Perform some Redis commands asynchronously
pipeline = r.pipeline()
pipeline.set('key1', 'value1')
pipeline.get('key2')
pipeline.incr('key3')
responses = pipeline.execute()

print(responses)

In the above example, the Redis client sends three commands to the server (SET, GET, and INCR) without waiting for a response after each command. The pipeline() method returns a pipeline object that allows multiple commands to be executed in a single round-trip to the server. The execute() method sends all the commands to the server and waits for the responses, returning a list of responses in the order that the commands were sent.