20% is a huge claim; the article doesn't specifically mention if it's attributed to Maria or what combination of factors. I for one have been too busy to test the 5.1 release candidates or to test out Maria to find out.

As to whether or not you should use fewer queries, that's debatable. You should definitely learn the most optimal way to store and index data, and of course the proper use of them in the queries you do use.

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