4xx indicate client errors (you need to change you request). 5xx are server errors. "410 Gone" would be a 'permanent' error.

> 4xx codes indicate a permanent error condition.

Not necessarily, and especially not 409 Conflict, which “indicates that the request could not be completed due to a conflict with the current state of the target resource.”

“Current state” being often mutable, 409 is not generally permanent. 410 Gone is permanent.