Comparison
Fan-out ingestionvsPublish-subscribe
Fan-out ingestion
six teams each built their own connector to the same production database and the DBA noticed before anyone else did.
One captured source feeding many independent consumers instead of each consumer extracting for itself. Consolidating on a single capture is usually right — one connection to the source, one interpretation of its quirks, one place to fix a bug — and it is why a shared change feed tends to become a platform team's product. The trade is that the shared feed becomes a coupling point, so its schema and its retention become everyone's problem at once.
Full entry →Publish-subscribe
you publish the event once and three different services each get their own copy without the publisher knowing they exist.
A pattern where publishers emit to a topic and every interested subscriber receives a copy. It removes the publisher's knowledge of consumers, which is what makes adding a fourth consumer a zero-change operation upstream. The trade is that nobody owns the contract, so a field the publisher considers cosmetic can be load-bearing for a subscriber it has never heard of.
Full entry →