The conclusion of the talk is that we should put more effort in carefully designing indexes. But how can we make sure the indexes are really used now and in the future? We need to write some tests for it.
So I wrote a small Python script to test index usage per query. This uses the JSON explain format available in MySQL 5.6. It's just a proof-of-concept so don't expect too much of it yet (but please sent pull requests!).
A short example: