HTTP 429

Rate limit exceeded

The account sent more requests in the current minute than its plan allows. The limit counts requests, not credits, across all of the account's keys.

"type": "https://ohlc.io/problems/rate-limit"

Why it happens

Bursting above the plan's per-minute limit: 30 on Free, 300 on Developer, 1,000 on Pro, 2,000 on Commercial and 10,000 on Scale.

Wait Retry-After seconds; X-RateLimit-Reset gives the reset as a Unix timestamp.
Spread requests out and batch up to 100 symbols per request.
See limits, or upgrade on pricing.