Sure, You can compare Cloud SQL vs Cloud Spanner and RDS vs Dynamo, but it makes more sense to just say "Postgres" and assume that the reader can figure out that it means "Whatever managed postgres service you want to use".
The entire point is that every cloud provider has a managed postgres offering, and there's no vendor lock-in. Though, technically, Dynamo does have a docker image you could run in other cloud providers if it came down to that, you'd get no support for it.
I don't think it's really relevant to compare plain Postgres to Spanner, most folks have no need for something like this. It is made for folks who need to do millions of ACID type transactions a second/minute from all over the globe, and have a globally consistent database at all times.
There's a reason why Google installed and built their own atomic clocks and put them in their datacenters, it is to facilitate global timekeeping for this type of services. Most likely 99.9% of the time this type of database is overkill, and also likely way more expensive than you need.
> It is made for folks who need to do millions of ACID type transactions a second/minute from all over the globe, and have a globally consistent database at all times.
I think just doing some (not necessary millions) ACID transactions over the globe and have consistent DB is strong value proposition even for small users.
The dynamodb docker image you’re referring to will get you shot if you try and use it in prod. It’s an API wrapper on top of sqlite and has a ton of missing functionality
There are a couple of databases out there with ddb compatible interfaces, like scylladb
