Concrete5 blocks use ADOdb Active Record. To function, Active Record queries a table's metadata to setup certain things for the object. You can cache this request to reduce the number of times ADOdb Active Record gathers this information.
If you don't already have one create a file named
Add this to it
<?php global $ADODB_ACTIVE_CACHESECS; // set to the number of seconds to cache metadata $ADODB_ACTIVE_CACHESECS = 600;
This will create files in you sites cache directory for each table used by ADODB Active Record for the time specified.
I should add that much of the benefit of this is superseded by block caching in general, but can be of benefit in certain situations.