The consumer's goal is stated as they would state it — things they can have now — which is why availability staleness is treated as a correctness problem rather than a freshness preference.
The merchant is a separate actor from catalogue ops because one checks their own change and the other changes two million documents; those are different requirements wearing one word, 'edit'.
The reconciler is in the cast because the platform's worst failure, a silently missing document, has no human complainant.
Assumptions
Search engineers own relevance and expect to ship weekly; SRE owns the index lifecycle and expects never to hand-edit a live index.
Source systems will accept emitting a change stream, but not a nightly full table scan of production.
