Question: When to use Memcached over Redis?

Answer

Both Memcached and Redis are in-memory data stores that can be used to speed up web applications by caching frequently accessed data. However, there are some key differences between the two that may make one a better fit for your particular use case.

Here are some situations where you might want to choose Memcached over Redis:

1. Simple Key-Value Caching: If you need to cache simple key-value pairs and don't require advanced features like data persistence or atomic operations, then Memcached may be a better choice. Memcached is designed specifically for this use case and has a simpler architecture than Redis, which makes it faster and more lightweight.

2. High Concurrency: If your application requires high concurrency and you need to handle a large number of simultaneous requests, then Memcached may be a better choice. Memcached is optimized for high-performance and can handle thousands of requests per second.

3. Large Data Volumes: If you need to store large amounts of data in memory (i.e. tens or hundreds of gigabytes), then Memcached may be a better choice. Memcached is more efficient at storing large data volumes than Redis, which can become slower as the amount of data stored increases.

Here's an example of how to create a Memcached client in Python using the python-memcached library:

import memcache

client = memcache.Client(['localhost:11211'], debug=0)

# Store a value in the cache
client.set('key', 'value')

# Retrieve a value from the cache
value = client.get('key')

In summary, Memcached is a good choice if you need to cache simple key-value pairs, require high concurrency, or need to store large amounts of data in memory. However, if you require advanced features like data persistence or atomic operations, then Redis may be a better choice.