A cache is useless if it serves wrong data. Picking the right invalidation strategy is key to system integrity.
1Lazy Loading (Cache-Aside)
This is the safest bet for most applications. You only cache what's requested, and you manually delete (invalidate) the cache key when the underlying data is updated in the DB.
2Proactive Sync (Write-Through)
If you have a high 'Read-after-Write' requirement (users expect to see their changes instantly), Write-Through ensures the cache is never behind the database.
3Asynchronous Speed (Write-Back)
For high-frequency writes (like counting page views), Write-Back allows you to batch updates and write them to the database every few minutes, drastically reducing DB load.
