OK I was likely able to solve it on our side (at least it looks like it, but need to wait 1-2 days if it happens again).

Reason is more or less described in this issue: https://github.com/aws/aws-sdk-js-v3/issues/6763

tldr:

in SDK V2

new S3({
  httpOptions: {
    timeout: 10 * 1000,
    connectTimeout: 10 * 1000,
  }
});

was used to configure the timeouts of the S3 client.

This was somehow supported for some time also in SDK V3 but suddenly was not supported anymore (around version 3.709 somewhere).

The correct way now is to configure the timeouts via

new S3({
  requestHandler: {
    requestTimeout: 10 * 1000,
    connectTimeout: 10 * 1000,
  }
});

in the S3 client.

See also: https://docs.aws.amazon.com/AWSJavaScriptSDK/v3/latest/migrating/notable-changes/ https://docs.aws.amazon.com/AWSJavaScriptSDK/v3/latest/Package/-smithy-node-http-handler/Interface/NodeHttpHandlerOptions/