We are continuously getting max connection errors on our site, (50k+ users per day), and the server admins pointed us to this query in your add-on, which is taking around 20 seconds to complete:
I've attached some screenshots.
SELECT conversation_master.*, conversation_user.*, conversation_starter.*, conversation_recipient.recipient_state, conversation_recipient.last_read_date FROM xf_conversation_user AS conversation_user INNER JOIN xf_conversation_master AS conversation_master ON (conversation_user.conversation_id = conversation_master.conversation_id) INNER JOIN xf_conversation_recipient AS conversation_recipient ON (conversation_user.conversation_id = conversation_recipient.conversation_id AND conversation_user.owner_user_id = conversation_recipient.user_id) LEFT JOIN xf_user AS conversation_starter ON (conversation_starter.user_id = conversation_master.user_id) ORDER BY conversation_user.last_message_date DESC LIMIT 40;