Basic Components Implementation

Question 1

How to implement LRU / MRU cache?

Answer 1

Hash Table + Link list

Question 2

How to implement LFU cache?

Answer 2

Hash Table + Sorted List
(similar to Redis sorted set)

Question 3

How to keep records from the last x secs or minutes?
What is the use case for this?

Answer 3

Redis Sorted set where the score is the timestamp.
ZREM RANGE BY SCORE
Use case: API Rate Limiting

Question 4

How to keep the rank of all players in a tournament?

Answer 4

Redis Sorted set where the score is the points (logN)
ZREM RANGE BY RANK
Use case: Lichess