A change made in 2024 to send identifiers rather than snapshots, and what a year of it produced.
average payload 12 KB → 0.6 KB
p99 200 KB → 1.1 KB
broker storage 41 GB → 2 GB
and the cost, which the 2024 note predicted and did not
quantify:
every consumer now does a lookup. 41,000 messages a
day × one query = 41,000 queries, all of them by
primary key, all of them under a millisecond.
which is nothing, and would not be if the lookup
crossed a network to another service.The lookup cost is trivial when the consumer shares a database with the producer and is the dominant cost when it does not, which means this decision is a property of the deployment topology rather than of message design. Having merged the services in 2024, the topology is favourable — and reversing that merge would make this change wrong.