The Must-Solve 150.
Every question is a real implementation, debugging or architecture task. Work through the levels in order, or jump straight to what your next interview needs.
10 of 150 questions
Medium
75 questions, 25–45 minutes each
Implement, then defend your edge cases, performance and tests.
Concurrency & scheduling
Pools, queues, rate limiters and batching with bounded concurrency.
- 46Implement mapLimit() / throttlePromises() with maximum N concurrent tasksFree
- 47Implement
promisePool()using worker loops - 48Implement an asynchronous task runner with configurable concurrency
- 49Implement a priority-based task scheduler
- 50Implement a queue supporting pause, resume, and clear
- 51Implement a token-bucket API rate limiter
- 52Implement a sliding-window rate limiter
- 53Implement request deduplication for identical in-flight API calls
- 54Implement a concurrency-safe async cache with TTL
- 55Implement batch API calls with maximum batch size and interval