Which data store to choose?

Question

NoSQL

Greetings. It is necessary to develop a cross-platform application for five operating systems (Windows, Linux, Mac, Android, iOS).
Q: Which data store should I choose? In particular, I choose a base: it is desirable, of course, one and cross-platform, but for efficiency, you can choose different ones for certain systems. It is possible that there are even better ways, for example, for mobile devices, save to local storage ... Not very competent in this matter, I will be glad for any useful ideas. Here is a list of my wishes for the database or other storages:
Mandatory requirements:
* storage of data of the form: key -> json object
* atomicity
* unlimited size of the database
Desirable:
* fast response to reading
* storage of the database file in the application folder
Полезные:
* умное кэширование в оперативной памяти
* репликация и разделение по частям

Answer 1

SQLite

Answer 2

https://postgrespro.ru/
https://postgrespro.ru/education/courses/DBA1