Hi @PedroReina !
We had the same need in the past and tried various approaches. As @danbjoseph said, querying json from central's database is not easy nor suitable.
OData API is the solution.
If your destination database is PostgreSQL, we published two years ago I created a set of function to automatically get data from central in our daily database.
pyODK offers now the possibility to create pl/python function within your own PostgreSQL database (we will show something soon), or python autonomous routines.