There's definitely a balance. I tend to be more concerned about things which store or update data durably — testing a Lambda function is relatively easy, and if you're calling other services but your code isn't a complete mess that's a relatively manageable problem, but something like DynamoDB poses both a migration challenge (especially for a running system) but also questions about correctness if you aren't really careful about how you handle things like concurrent access. That doesn't mean they're not worth using but it definitely tells me where you want robust validation, testing, etc. since it's a lot harder to recover from missing/corrupted data than it is to resolve a 500 error on a particular endpoint.