500kb in 3 minutes sounds good so far, i think

You could use an sqlite databse, for instance. This stores the whole data in a file and you can run select-statements. I've also developed a small management system which could be used (supports filtering, sorting, etc.), but if you need support for real database features (views, triggers, etc.) you should prefer using sqlite in this case.
But I think this would be a better solution for your project instead of an extra mysql server.

Regards
TSGames