For us, it is very important to get high response time for our website php script which queries a large database. It is essentially getting user information for the user who visited the page. There may be millions of users in the db.
We would like to not bother using the user data at all if the record is not already in the InnoDB Buffer Pool of the MySQL database, and use information only if present in the above cache.
Is there a way to directly ask Mysql/InnoDB whether the record is in cache?