Well, no, he is wrong. Postgres can run on either x86 or ARM. You can do replication between them, no problem. There's no reason to run workloads on x86 just to get access to larger instance sizes at some point down the road. You can migrate Postgres on ARM to Postgres on x86, it's not even hard. Use what works best for you now and in the part of the future you have some visibility on. AWS might well announce bigger Graviton instances before you ever get there, if you ever get there at all.
