Function is_slot_active_error 

pub fn is_slot_active_error(err: &FaucetError) -> bool

Returns true if err is Postgres reporting that the replication slot is still active — held by a backend that has not yet released it. Postgres raises “replication slot "…" is active for PID …” (SQLSTATE 55006).

This is transient on a rapid restart: a scheduler or serve re-running the pipeline before the previous connection’s backend has fully exited finds the slot momentarily still in use. It clears within a short window, so it is safe to retry after a backoff (#146 M12).