added indices and cleaned up notification

I'm interested in hearing the rationale for the two multiple-column indeces above.  The single column ones seem easy to justify, because they are fields with many values used for frequent lookups.  Did you also consider an index on actor_id?

Both the "draft" and "field" columns are used frequently, too, but since there will be few "draft" values for a given "card_id" and few "field" values for a given card_action_id, my first (undereducated) impulse is to say that I'd be surprised if they actually sped things up much.

But I'm far from a db optimization expert.  Perhaps the combinatorial effects are worth it since we so often query these in combination?  It might be worth a few experiments...

This post might be useful if you haven't seen it: http://stackoverflow.com/questions/687986/what-are-some-best-practises-and-rules-of-thumb-for-creating-database-indexes