Caiso Rate Limits

CAISO publishes no numeric rate limit, quota or burst allowance for the OASIS Download API, but it does enforce one at the edge. Its published API Terms of Use prohibit "Adverse and Excessive Use" and reserve the right to suspend or terminate access for callers who impact system performance. In practice the F5 BigIP in front of oasis.caiso.com answers a request that arrives too soon after the previous one with HTTP 429 and the plain-HTML body "CAISO Acceptable Use Policy Violation. Please retry your request after 5 seconds." — so the operative published limit is the five-second spacing named in that response body. This was verified live: two identical, valid SingleZip requests issued back to back returned 200 then 429, and the same 429 is returned for malformed/parameterless requests to the servlet. No X-RateLimit-* headers and no Retry-After header are returned; the retry interval is only in the body text. The Today's Outlook CSV feeds under www.caiso.com/outlook are served from the web tier and no throttling was observed on them.