Drupal 7 forms using FAPI #ajax automatically cache forms in cache_form for normal form_state operation and all that. There is talk about this elsewhere (https://drupal.org/node/1506196 and http://stackoverflow.com/questions/4709290/help-drupal-cache-form-table-...), but that's not the point of this here.
With two servers, master and failover, we have mysql binary logging every transaction on master for replication by failover. Binary logging does not permit specification of which tables to track and not -- it's all or nothing. Our replication requires binary logging. The issue has arisen that a couple forms using ajax happen to have particularly large lists of select options (states in the united states and stores within in each state), and these form elements are cached in cache_form. .. and these {cache_form} table writes are logged in binlogs.. and the mysql hdd and nagios have become fast friends with frequent correspondence back to the server admin team.
I think a basic solution might be to switch from db cache to file based cache, but I wonder if there's not a better, less specific-to-my-problem solution with, say, how the forms are built or something?
Thanks
-Bronius
