Why Am I Seeing the Error Message "Backend unavailable" or "Backend timeout" When I Invoke the Backend Service?

The backend service address is incorrect.

Change the backend service address in the API definition.

If the domain name is used, ensure that the domain name can be correctly resolved to the IP address of the backend service.

The timeout duration is incorrect.

If a backend service fails to return a response within the configured timeout duration, APIG displays a message indicating that the backend service fails to be invoked.

Increase the backend timeout duration in the API definition.

If the backend address is an ECS address, the security group to which the ECS belongs may block the request in the inbound or outbound direction.

Check the security group to which the ECS belongs and ensure that the inbound and outbound port rules and protocols of this security group are correct.

The request protocol is incorrect. For example, the backend service uses HTTP, but HTTPS is selected on APIG.

Ensure that the protocol of the created API is the same as that of the backend service.

The backend service URL is unreachable.

Check the URL.