Can in-memory SQLite databases scale with concurrency?
The answer is no. I asked on the SQLite user group and got the following response from Pavel Ivanov:
No, SQLite doesn't support full concurrent access to any database. The only concurrency you can earn is having on-disk database without shared cache (so actually having several copies of the database in memory). Of course I don't consider option of concurrency from different processes.
If you set the page size and cache size large enough to contain the entire database, read operations will be fulfilled from the cache and the performance will be nearly equal to an in-memory database.