Tuning MySQL and the Ghost of Index Merge Intersection

Don't have this in your query/app: "AND DeleteAt = 0"

If your app must depend on that,put the delete posts in a deletepostsID table and do a join.

IIRC its because mysql queries can only use one index at a time (per table) and any type of binary/enums/ 0 /null tables will always force a full table scan regardless of indexes