Backend & systems·Caching and invalidation
you write to the cache, return success immediately, and let a background flush push the batch down to the database later.
Write-behind cache
Also calledwrite-back cache
Writes land in the cache and are persisted asynchronously, usually coalesced into batches. It absorbs write spikes and can collapse many updates of the same key into one store write, which is why counters and metrics use it. The exposure is real data loss: anything acknowledged but not yet flushed dies with the process.