What DBMS to take to store user data?

Question

Database

Hello, such a question, there are many applications with different requirements for user data, for example, one application requires the user to specify a phone address and date of birth, and another application stores about 15 different fields, these data and requirements may change as applications change or as they are added new ones with their own specific functionality. They should be united by a single user base with all their data. 
The idea is as follows: to store authorization data in a relational DBMS (MySQL for example), but I think to store all other data in some key-value storage. but not exactly key-value 
since there should be a search in the storage by 2 parameters (user_id, domain). Which of the existing solutions can you recommend? I read about non-relational databases like redis, mongo, but I can’t decide which will be better in terms of performance, scalability, the ability to make actual backups (something like replication)

Answer 1

In my opinion it is easier to store everything in one DBMS. Both MySQL (5.7+) and PostgreSQL (9.2+) support the JSON storage type and allow you to search by their keys.

Answer 2

You have a bunch: user->application->(domain)->data.
So you can use any type of database: it will not affect the speed in any way.

Answer 3

Here is another look. www.keycloak.org/index.html