NO_HEALTHY_KEY

HTTP 503Auto-retry

All keys for this vendor are unhealthy; failover engaged.

By default a failed call returns a result with an error instead of throwing, so your business flow is never interrupted.

Rate-limit and upstream errors are retried automatically with backoff, honoring the Retry-After header.

Published error codes are permanent: their meaning never silently changes, and deprecated codes keep returning for at least 12 months.