Checks if a job can be enqueued based on concurrency limits.

Returns {:ok, :ok} if allowed.

If the limit or throttle is exceeded, or the advisory lock could not be taken, the result is {:ok, {:error, reason}} where reason is :limit_exceeded, :throttle_exceeded, or :lock_failed. That shape comes from Ecto.Repo.transaction/1 wrapping the callback return value (not a rolled-back transaction).

Checks if a job can be performed based on concurrency limits.

Returns {:ok, :ok} if allowed.

Otherwise returns {:ok, {:error, reason}} with reason in :limit_exceeded, :throttle_exceeded, or :lock_failed (see check_enqueue_limit/2 for why this is {:ok, {:error, _}}).