ذاكرة المستوى الثاني وذاكرة الاستعلامات المؤقتة

في هذا الدرس

decide whether a cache is worth it.

الموضوعات المخطط لها

• First-level cache: the persistence context, per transaction; always on.
• Second-level cache: shared across sessions through a provider (Ehcache, Infinispan, Caffeine via JCache); needs @Cache per entity.
• Good candidates: read-mostly reference data (countries, categories). Bad: frequently changed or large mutable entities.
• Query cache stores result ids and is invalidated on any write to the tables involved; rarely a win.
• Multi-instance deployments need a distributed or invalidating provider; often a dedicated cache (Redis, later modules) is simpler.
• A cache hides bugs and adds staleness; measure hit ratio before keeping it.