Store hundreds of tasks per day per user in custom log sub-system

[eluser]CARP[/eluser]
[quote author="CroNiX" date="1408116958"]Yes, CI has a SQLite driver included. But why not just continue to use MySQL since you are already using it? As long as it's properly indexed, millions of records shouldn't be an issue.[/quote]

That's the idea, but I'm not used to "bigdata" and would like to learn and be sure that I'll be able to store a couple of millions of records (accumulated in a year, for eg.) in this "log" table without affecting the whole app's performance

Which changes and which indexes would you create to this table?

Thanks again