Design a simple in-memory key-value store (like a tiny Redis) for a single server, exposing GET, SET, and…

Question

Design a simple in-memory key-value store (like a tiny Redis) for a single server, exposing GET, SET, and DELETE over a network API. It should hold a few million keys, support optional per-key TTL expiration, and survive a restart by reloading recent data. Discuss the data structures, how TTL is handled, and how you'd persist data so a crash doesn't lose everything.

Prep Room · Answer

I'd build the whole thing around a single in-memory hash map from key to value, which is what gives us O(1) average GET, SET, and DELETE. Alongside each value…

In-memory key-value store