The 10 most important things to prepare about caching if you are appearing in a software engineer interview, especially backend are the following.

1. What can be cached — Client, Server, In Between (Server-Database ), API, Hardware (CPU). Operations that are used frequently, heavy operation/computation;
2. Cache — Hardware or software that stores the data to provide faster access (the result of the heavy computation, API responses, API requests);
3. Write through cache — when the cache is updated in cache and memory synchronously, recover data if the process dies. Pros — simpler and reliable; cons — better works when not so many writes in cache;
4. Cache Hit— find requested data in the cache
5. Cache miss — did not find stored cache because of pure design
6. Cache eviction policy — rules when cached will be removed (LRU (recent), LFU (frequent), FIFO (queue))
7. Content Delivery Network (CDN) — third party service that caches your server (based on region), always better latency. PoP (Point of Presence). Cloudflare, Google Cloud CDN.
8. Write back cache — when cache updated in cache and memory asynchronously;
9. If we care of the staleness of cache (accuracy of data) -> we use local cache; if accuracy is important (views, likes) — use third party cache (Redis)
10. Golden Rule: Not every time, when optimizations are needed to be done and caching is the perfect solution.