There are a couple of reasons you want to avoid this. For one, there’s no way to know if a row is locked for update. So you could have 2 consumers read some data, request the update lock, do a lot of work, then line up behind each other to update those rows with the same exact data. This duplication of effort will get worse as the system scales. In fact, this doesn’t ensure that there will only be one consumer, which will disqualify it as a solution in many instances.