As fas as I understand, the SQLite "file" can be accessed safely by different processes.

Maybe it can be accessed by more than one process, but that does not mean it should be. Consider using a "real" database server if you need multi-process access to the database.

I would recommend using PostgreSQL. Here is why: Re^2: What is the best Perl library to use to connect and access MSSQL2008 Database from winXP PC?, Re^2: Perl and Database, Re^2: What is your favourite Linux or cross-platform database?. PostgreSQL runs on Unix (including MacOS X, Linux) and Windows, and is quite easy to set up and run, and it comes with excellent documentation. You may also want to install PgAdmin.

Alexander