Yes. 4xx codes are client errors: The request contains a mistake or can't be fulfilled as sent.

4xx · Client error

HTTP 409 Conflict

The request conflicts with the current state, such as an edit collision or a duplicate unique value.

Example response

HTTP

HTTP/1.1 409 Conflict
Content-Type: application/json; charset=utf-8

{ "error": "Conflict" }

Look up the headers shown here in the HTTP headers reference.

What does HTTP 409 mean?: Conflict. The request conflicts with the current state, such as an edit collision or a duplicate unique value.
Is 409 an error?: Yes. 4xx codes are client errors: The request contains a mistake or can't be fulfilled as sent.