Isn’t a “local emulator of cloud services” kind of the perfect project to be vibe coded? Extremely well documented surface to implement, very easy to test automatically and prove it matches the spec, and if you make some things sub optimal performance wise, that is totally fine because by project will not be used in a tight loop anyway - e.g. it will just need to be faster than over the network hop plus the time it takes for the cloud to actually persist things. This can just need to do this in ram and doesn’t need to scale.

So I’m shocked cloud providers haven’t just done this themselves, given how feasible it is with the right harness

AWS _does_ officially provide local-first dev containers for services like DynamoDB but sadly not every AWS service comes with those. Why? I have no idea, like you said it's clearly feasible and they already do it for some services today...