Service Unavailable — retryable. Two conditions land here:
- Transient dependency — a database connection, the model behind filter generation, or another
dependency was briefly unavailable.
- Request budget exhausted — the request's own wall clock ran out before the filter could be given a
fair slice, so no records were read. The time went elsewhere in the same request: a slow generation
call, or earlier pages of the same projection.
The second case is the OPPOSITE of the 422 that says the filter "took longer than 10s to evaluate". That
422 is a statement timeout and is deterministic — the filter selects more than can be evaluated, and an
unchanged retry fails identically. This 503 makes no such claim about the filter, so retrying is worth
doing; if it recurs, narrow the filter or ask for fewer records per call.
