conflict
What happened
Section titled “What happened”Conflict. The operation could not be completed.
Technical background
Section titled “Technical background”ConflictError is the generic 409. Its subclasses carry a narrower code:
version_conflict,
precondition_failed,
record_locked,
idempotent_replay and
unique_violation. Handlers can match the
subtype with instanceof, the HTTP layer treats all of them as 409.
Re-read the current state, then decide whether the request still makes sense.