1 min lesson
Fan-out and per-consumer limits
Work through the cases in "Fan-out and per-consumer limits", pairing each signal with the move that fits.
Step 1 of 2
Fan-out and per-consumer limitsstop one slow endpoint from taking everyone down
One event often has many destinations - an SCM push might notify an indexer, a build trigger and an audit log. Fan-out duplicates the event onto separate per-consumer queues so each subscriber moves at its own speed. The reason this matters is failure isolation.
Shared queue, no isolation
One slow consumer backs up the head of the line.
A failing endpoint's retries starve healthy ones.
Head-of-line blocking turns one bad subscriber into a global incident.
Per-consumer queues + concurrency caps
Each subscriber has its own backlog and its own pace.
A cap on in-flight deliveries per endpoint contains a slow one.
A broken endpoint fills only its own queue and DLQ.