How to make JOINS faster?

I had this query to start out with: ``` SELECT DISTINCT spentits.* FROM `spentits` WHERE (spentits.user_id IN (SELECT following_id FROM `follows` WHERE `follows`.`follower_id` = '44' AND `follows`.`accepted` = 1) OR spentits.user_id = '44') ORDER BY id DESC LIMIT 15 OFFSET 0 ``` This query takes `10ms` to execute. But once I add a simple join in: ``` SELECT DISTINCT spentits.* FROM `spentits` LEFT JOIN wishlist_items ON wishlist_items.user_id = 44 AND wishlist_items.spentit_id = spentits.id WHERE (spentits.user_id IN (SELECT following_id FROM `follows` WHERE `follows`.`follower_id` = '44' AND `follows`.`accepted` = 1) OR spentits.user_id = '44') ORDER BY id DESC LIMIT 15 OFFSET 0 ``` This execute time increased by `11x`. Now it takes around `120ms` to execute. What's interesting is that if I remove either the `LEFT JOIN` clause or the `ORDER BY id DESC` , the time goes back to `10ms`. I am new to databases so I don't understand this. Why is it that removing either one of these clauses speeds it up `11x` ? And how can I keep it as is but make it faster? I have indexes on `spentits.user_id`, `follows.follower_id`, `follows.accepted`, and on `primary ids` of each table. EXPLAIN: ``` 1 PRIMARY spentits index index_spentits_on_user_id PRIMARY 4 NULL 15 Using where; Using temporary 1 PRIMARY wishlist_items ref index_wishlist_items_on_user_id,index_wishlist_items_on_spentit_id index_wishlist_items_on_spentit_id 5 spentit.spentits.id 1 Using where; Distinct 2 SUBQUERY follows index_merge index_follows_on_follower_id,index_follows_on_following_id,index_follows_on_accepted index_follows_on_follower_id,index_follows_on_accepted 5,2 NULL 566 Using intersect(index_follows_on_follower_id,index_follows_on_accepted); Using where ```