Caching Strategies and In Memory Storage Questions

Caching strategies for improving performance and reducing latency: HTTP caching semantics (Cache-Control, ETag, conditional requests, Vary), application-level caching with Redis and Memcached, in-memory data structures for caching, cache eviction policies (LRU, LFU, FIFO), cache invalidation strategies, TTL selection and trade-offs, and the consistency and performance implications of deciding what and when to cache.