caching

Spring Cache abstraction simplifies caching with annotations. @Cacheable caches method results—subsequent calls with same arguments return cached values. @CachePut always executes methods and updates cache. @CacheEvict removes entries or clears entire

ETags are a low-effort way to cut bandwidth and CPU when clients poll for resources that rarely change. The server computes an ETag for the representation (often a version, content hash, or updated_at value) and compares it to If-None-Match. If they m