HTTP 503 Service Unavailable

What HTTP 503 Service Unavailable means

503 Service Unavailable means the server is temporarily unable to handle the request — usually because it's overloaded or down for maintenance. It's meant to be transient, and a `Retry-After` header may say when to come back.

Which category is it?

503 is a 5xx code — Server error. 5xx means the server failed to fulfil an apparently valid request. It's the server's responsibility, not the caller's.

Common causes

• The server is overloaded or out of capacity
• Planned maintenance
• A dependency the app needs is unavailable

How to fix it

• Retry after the `Retry-After` interval
• Scale up capacity or add load shedding
• Check that required dependencies are healthy

Other server error (5xx) codes