Using Memory table as a cache for InnoDB table

[Ya Wi]

Hi all,
I'd like to know if somebody has already successfully implemented following concept :

- an InnoDB table stores some statistics about users ;
- to avoid a lot of updates on it, I maintain a similar memory table and execute update queries again this table instead of real one ;
-every X minutes, I update InnoDB data with Memory data (only 1 update).

I could save many updates on InnoDB table and some IO operations.
But I am afraid about table locking system of Memory table.

Many thanks,