In any sort of Mobile/Web combo application, how would they synchronize the data between the 2 databases?

All:

We have a software application with

1) Web-based component
2) Mobile-based component

Our 1) Web-based component uses

a) MongoDB as the Database

b) ASP.NET C#

Our 2) Mobile-based component uses

a) Java

b) SQL Lite

However, both the databases have the same tables, but we have Not created any sort of bridge table between the collections in MongoDB and the tables in the SQL Lite.

In any sort of Mobile/Web combo application, how would they synchronize the data between the 2 databases? I'm looking for typical solutions that the software industry uses.