Interesting — those are the ones that depending on the case, approximating them with local redis/postgres/vms without the AWS specific APIs on top is often good enough — because my app is just talking to them over native protocols anyway.

Or I am doing something so specific, that a local emulation of the aws api isn’t ever going to be good enough, so there’s not a lot of point in trying. For example, writing code that handles automatically spinning up RDS instances from an RDS snapshot — a local emulation of that process is going to be so far off from what would actually happen no matter what they do.

I'd put ALL the ones listed above: SQS, S3, KMS, DynamoDB, EC2, RDS, Redis in the required "core" services column, and also throw in IAM, SNS, and SecretsManager as well. Those are all table stakes imho.

I'm using all of the above in LocalStack today. Frankly, I don't believe this is as "impossible" a task as several in this thread are insinuating. It's the type of rote work you can delegate to AI to build these days, as observed in this OP.

Building a test suite to validate the state-transient mocks in question against the real deal is not difficult. Only annoyingly expensive (in time and money) if run often, which is exactly the problem they're solving.