Why do we have Redis when we have MySQL temporary tables?
<p>MySQL temporary table are stored in memory as long as computer has enough RAM (and MySQL was set up accordingly). One can created any indexes for any fields. </p>

<p>Redis stores data in memory indexed by one key at time and in  my understanding MySQL can do this job too.</p>

<p>Are there any things that make Redis better for storing big amount(100-200k rows) of volatile data?  I can only explain the appearance of Redis that not every project has mysql inside and probably some other databases don't support temporary tables.</p>

<p>If I already have MySql in my project, does it make sense to put up with Redis?</p>