Serverless is more expensive than you'd expect (2021)

The stack I'd recommend is a mixture of containers and cloud-native "transparent" assets, so something like ECS + RDS + a CDN + DNS-based service discovery is a good middleground.

RDS is an excellent example of a cloud-hosted service that implements an open standard. Even if your production uses RDS, you could still reproduce bugs somewhat easily using a postgresql docker container seeded with something similar to production data.