A simple custom SaaS database?

Question

Database

Tell me SaaS database options in which you can configure:
- the number of tables, relationships and fields in them
- differentiate access to read / write
- with a minimal user-friendly interface
Desirable:
- API
- complex validation
- events for changing data
Now for this use clientbase. In many ways it is convenient, but there are some complaints.
I thought that 100% there are some foreign analogues (and possibly ours).
It is required to enter data for some new Business Process, where roles are already needed and Google Doc does not help, but it is too early to enter into the main automation system.

Answer 1

There was a similar thing: Zoho Creator.
MS Access Online might be good too

Answer 2

with minimal user-friendly interface

What is this for?
Services like OpenShift do not suit you? there are built-in Postgre, Mongo, Mysql, etc