Messaging & Streaming

Move work off the synchronous request path and decouple producers from consumers, so a slow, spiky, or failure-prone operation doesn't block the caller. Getting this wrong is subtle: a queue silently changes the delivery and ordering guarantees, and under load it can absorb a spike gracefully or become the thing that hides a meltdown until the backlog is unrecoverable.

When to reach for this

A step is too slow to do inline (image transcode, fan-out, third-party call); the write path is spiky and needs a buffer to smooth bursts (→ back-of-the-envelope for the spike factor); two services must be decoupled so one can fail or deploy independently; or many consumers need the same event stream. The async hand-off buys responsiveness, isolation, and elasticity (scale producers and consumers separately).