How to Design a Distributed Caching System like Redis or Memcached

STEP 1: Talk on Features and Expectations

Caching allows us to reuse previously retrieved data.

A. LRU Eviction Policy

We might face a scenario when we have to remove older entries to accommodate continuously incoming entries. So it would be better to have a data structure that can give me least recently used objects so that it would be easier for me to remove those entries. 

Study more about LRU cache here.

Step 2:  System requirement and Scalability