Backend Interview Challenges
94 challenges94 challenges · 5 free to solve now · code rate limiters, caches, concurrency, distributed systems, and more.
- 1EasyLRU cache (O(1) get/put)Free
Fundamentals
- 2MediumLFU cacheFree
Fundamentals
- 3MediumSliding window rate limiterFree
Fundamentals
- 4MediumToken bucket rate limiterFree
Fundamentals
- 5MediumLeaky bucket rate limiterFree
Fundamentals
- 6EasyIn-memory message queue (FIFO) Premium
Messaging
- 7MediumPBKDF2-SHA-256 password hashing Premium
Security
- 8EasySQL: top-N per group (window fn) Premium
Databases
- 9EasyStructured logger (JSON) Premium
Observability
- 10MediumTCP echo server (raw socket) Premium
Networking
- 11MediumThread-safe bounded queue Premium
Concurrency
- 12MediumJWT verify + sign (HS256) Premium
Security
- 13HardLeader election (Bully / Raft-lite) Premium
Distributed Systems
- 14EasyMetrics: counter / gauge / histogram Premium
Observability
- 15HardReader-writer lock Premium
Concurrency
1–15 of 94