What it means

A 503 Service Unavailable response indicates the server is currently unable to handle the request, usually because it is overloaded, undergoing maintenance, or being deployed. The condition is meant to be temporary.

Common causes

• The server is overloaded with traffic.
• Scheduled maintenance is in progress.
• A new deployment is restarting services.
• An autoscaling group has not yet brought up enough capacity.

How to fix it

• If you are a visitor, wait a few minutes and try again. Check the Retry-After header for guidance.
• If you are the site owner, check server load and scale up if needed.
• Verify the maintenance window is over.
• Review your autoscaling and load balancer configuration.