> provide Postgres or similar as a database choice
Amplify's core architectural presumption is to only use serverless options to try to keep costs low. Serverless SQL databases are currently a big hole in AWS's offering. Yes, there's Aurora Serverless, but you need to run it in a VPC, you can't scale to zero (so, for some definitions, not really serverless), v2 threw out their Data API, and v1's Data API had severe scaling issues anyway. v2 is so expensive that you have to very seriously think through the numbers on the small RDS databases and ask what value you're actually going to get out of v2. So what OP proposes can't really be done by the Amplify team.
That said, the fact that Planetscale and Neon (which also have branching!) continue without serious competition from AWS is a serious headscratcher.
That said, nothing prevents you from spinning up services/endpoints that lean on whatever datasource you care about. Assuming it's accessible within the VPC you can shove all your data in there and call it a day.
You have another potential problem in your stack, but it can be done.
Of course it can be done, but the minute that you need to spin up a VPC, your infrastructure complexity becomes considerably higher. You need to worry about subnetting, carving up IP address space and IPv4 vs. IPv6, making sure you set up VPC Service Endpoints for various AWS services so that you're not paying for Internet egress despite using AWS services, security groups... none of which relates to business value at all.
It's just a hassle that's best avoided unless you really don't have any other choice or the financial math actually works out for doing so.
Amplify's core architectural presumption is to only use serverless options to try to keep costs low. Serverless SQL databases are currently a big hole in AWS's offering. Yes, there's Aurora Serverless, but you need to run it in a VPC, you can't scale to zero (so, for some definitions, not really serverless), v2 threw out their Data API, and v1's Data API had severe scaling issues anyway. v2 is so expensive that you have to very seriously think through the numbers on the small RDS databases and ask what value you're actually going to get out of v2. So what OP proposes can't really be done by the Amplify team.
That said, the fact that Planetscale and Neon (which also have branching!) continue without serious competition from AWS is a serious headscratcher.