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Failure Modes

Upstream Timeout or Error

  • Upstream queries are bounded by a timeout; on timeout or error, the behavior below applies.
  • If stale cache is available, ResilientDNS serves it immediately and schedules a background refresh.
  • If no cache entry exists, ResilientDNS returns SERVFAIL.

Refresh Behavior

Refresh failures do not block requests. They only affect logs and metrics, and the resolver continues to serve cached responses when possible. Refresh is best-effort with no retries or fallback.