Json schema validation is cpu expensive in nodejs, so you do not want it in production for every request. We made a proxy [1] that only allows requests that are conform to the swagger json which is easy to hook between frontend and backend in dev-mode
I wrote a master thesis where I compared several realtime database products. I promise you amplify is no where "getting there". It is a crippled version of firebase and there is no fix in sight. For example you cannot even do sort-queries with datastore or Amplify is not working with angular because they have broken typings since 9 months with no fix. And the list goes on..
[1] https://github.com/EXXETA/openapi-cop