NoSQLIntermediate
What is Redis good for beyond caching?
“Name uses of Redis that are not caching, with the data structure each relies on.”
What this tests
- Redis data structures
- Atomic operations
Answers by level
Read the beginner answer first and notice what is missing.
Rate limiting (INCR + EXPIRE, or a sorted set for a sliding window), leaderboards and ranks (sorted sets, O(log n)), sessions (a hash with TTL), queues (lists, or streams for at-least-once), distributed locks (SET NX EX), pub/sub fan-out, and atomic counters (INCR).
It is single-threaded, so every command is atomic without locks — that is what makes these primitives correct.
Green flags · Red flags
Strong green flag · Explains why atomicity comes from single-threading.
Green flags
- Names structures per use case
- Knows single-threaded → atomic
- Sorted set for leaderboards/rate limits
Red flags
- "Redis is just a cache"
- Only knows GET/SET
Follow-up questions
F1
Implement a per-user rate limit of 5/min.
Scenario
You need a real-time leaderboard for millions of players. Why is a sorted set better than a SQL ORDER BY?