[basicallybones]

Take this with a grain of salt, as I have not used PG Task Queues. I think the answer is there is no right answer here, and that it depends on your personnel and your data integrity/uptime guarantees. If anything, I suspect the only real "mistake" is using something like Kafka unless you really need it, but it's probably not that costly if you do.

Presumably, one easily could deploy a second PG to scale Task Queues independently of the DB layer as needed. So in that respect, there is no real issue, and it might be easier to start off with a single instance and split it up as needed for scale.

The real difference is if you find yourself dealing with subpar decisions from clueless management. Not giving them (or letting them know about) the option to put the queue and DB on the same instance can save your platform from total outages (especially if the queue load is much more variable than the DB load).