How to use Django's index_together for query both with filter and order_by?

If a query does not use any indexes at all, that's often because there isn't enough data in the table for an index to be really useful. However with 500 records there is a good chance that an index ought to come into play.

In the query that you have used, the appname_record_user_id_3214bab8a46891cc_idx is indeed a likely candidate but it's still not used. Why? because your query apparently causes the database to look at approximately half the table, as such an index cannot speed things up.

You seem to be on the right track with dropping one index. Two many similar indexes aren't really usefull either. I would try this index instead:

class Meta:
    index_together = (
        ('user', 'time','action'),
    )

The difference here is in the order of the fields. This is important:

MySQL can use multiple-column indexes for queries that test all the columns in the index, or queries that test just the first column, the first two columns, the first three columns, and so on. If you specify the columns in the right order in the index definition, a single composite index can speed up several kinds of queries on the same table.

I found the solution, it is not elegant, but it worked for me. Since I couldn't build any query, which will use 3-column index, I jush dropped a 2-column, so now both of my queries use 3-column. Have no idea, why it was ignored previously. Maybe, some complex mysql optimizations.