One wide event per request instead of ten log lines
Ten narrow log lines per request repeat the timestamp, the service and the request id ten times, and most backends can't join them. One event at the end of the request with every field on it is smaller, and answers questions the lines never could.
ctx.event.batch_size = items.length;
ctx.event.items_failed = failures.length;
// emitted once, in the middleware's finally"Which tenants had slow requests with more than ten queries on version 4.2" turns into a where clause.
observability
Longer version: the post this came from.