Spark Platform Rate Limits

Spark Platform publishes no numeric request-rate limit. What it publishes is the throttle signal (HTTP 429 with Spark error code 1550 "Over rate limit") and a set of hard per-request ceilings on the pagination parameters, which are the only numbers FBS states in the open. The request-size ceilings differ by key role: a standard key may ask for at most 25 records per request, a replication-role key up to 1000. Long-running requests are cancelled server-side rather than queued (codes 1515 and 1516). No RateLimit-* or X-RateLimit-* response headers are documented, so a client cannot see its remaining budget — it learns by being refused.