I’ve seen databases with 80K songs and more, using mt-daapd and sqlite2.
All worked nicely. Sqlite3 should be superior, so that’s not the issue.
As with routes and networking…. There should be a default route, and since DAAP works via multicast, you shouldn’t actually be sending multicasts over the VPN, unless it’s a bridged VPN.
Then again this boils down to the default route option.
The better solution perhaps would be to run the VPN on an extra network device, and binding the music server to the standard interface, not the VPN one.
Also, there are no plans for a “bigger” database backend. As far as I know Ron talked about bringing the gdbm backend back, which is a lot faster on embedded devices than sqlite. But I think it would be rather easy to fork and build it with MySQL support. There are only so much database operations, and they are encapsulated rather well.