Cloud Run: 503 Service Unavailable — The request was aborted because there was no available instance
Cloud Run could not serve the request: no instance was ready, instances crashed, or the service hit its max-instances/concurrency limit.
The request failed because either the HTTP response was malformed or connection to the instance had an error503 Service Unavailable Cloud RunThe request was aborted because there was no available instanceCloud Run 503 no available instanceThe request failed because the instance had an error Meaning
Look at the logs (Container called exit(1), OOM, startup probe failed) and at metrics for instance count and concurrency. 503 with "no available instance" means scaling limits (--max-instances), slow cold starts or quota; with "instance had an error" the container crashed while handling the request.
Common causes
- max-instances reached while traffic spikes
- Container crashing (exit, OOM, unhandled exception)
- Slow startup beyond the startup probe window
- Concurrency set too low for the load
- Regional quota or CPU allocation limits
⚡ Quick fix
- Raise
--max-instances/--concurrencyappropriately - Read Cloud Logging for the crash reason
- Use
--min-instances 1to avoid cold starts and fix startup time
Detailed fix by platform
gcloud
gcloud logging read 'resource.type="cloud_run_revision" AND severity>=ERROR' --limit 20
How to diagnose
- Message — No instance or instance error?
- Limits — max-instances/concurrency?
- Logs — Crash or OOM?
🔧 Still not fixed?
Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:
Similar errors
- 502 Bad Gateway: failed_to_connect_to_backend Google Cloud Load Balancing: 502 Bad Gateway — jsonPayload.statusDetails: failed_to_connect_to_backend / backend_connection_closed_before_data_sent_to_client
- Cloud Run 403: Your client does not have permission to get URL Cloud Run: Error: Forbidden — Your client does not have permission to get URL / from this server
- Cloud Run 504: The request has been terminated because it has reached the maximum request timeout Cloud Run: 504 Gateway Timeout — The request has been terminated because it has reached the maximum request timeout
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Other ways to find it
Where this error sits
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Last updated 4 Nov 2026