Re: MySQL 5.1 does not seem to be using the index that I expect it to.

[Rick James]

I assume you are referring to

select  id, trigger_time, note, type, status,
        notification_status, submission_id,
        actor_id, actor_display_name, actor_user_type,
        recipient_id, recipient_display_name,
        recipient_user_type, system_id,
    from  activity_event
    where  recipient_id=1
## without this:      and  status=1
    order by  trigger_time desc, id desc;   -- Still with DESC on both??

What do you get for this?

EXPLAIN
select  id, trigger_time, note, type, status,
        notification_status, submission_id,
        actor_id, actor_display_name, actor_user_type,
        recipient_id, recipient_display_name,
        recipient_user_type, system_id,
    from  activity_event
    where  recipient_id=1
    order by  trigger_time ASC, id ASC;

(Use [ code ] before, and [ /code ] after (without spaces).)