Caching interview questions

Implement a cache whose entries expire a fixed time after their last access, not after being set.

Implement an async memoize that caches results by key for a TTL and coalesces concurrent calls for the same key.

Cache responses by URL and revalidate with an ETag, reusing cached data on a 304 Not Modified.

Dedupe by idempotency key: run a task at most once per key, cache the result with a TTL, and retry on failure.

Store entities flat by id, normalizing nested relations and merging updates immutably.

Implement singleflight so concurrent calls for the same key share one in-flight promise instead of duplicating work.

Return cached data instantly, serving stale values while revalidating them in the background.

Batch and cache load(key) calls made in one tick into a single batch function call, preserving order.

Build a framework-agnostic query cache with request dedup, staleTime, subscribers, and invalidation.

Build a search box that caches results per query and dedupes in-flight requests.