Comparing maxscale's supported query hints to the ones from mysqlnd_ms, I noticed the latter has a switch to route queries to the last used server (http://php.net/manual/en/mysqlnd-ms.quickstart.sqlhints.php).

It would be nice to have such a hint in maxscale as well. It would enable usecases where you want to keep reading from the same master/slave, and also potentially a weaker variant of the Consistent Critical Read Filter.