I am working on a greenfield project right now utilizing MemSQL and so far its pretty solid. We haven't gone to production yet, so no concrete results to report.
The cool thing about it, compared to other in-memory tools, is that its communications protocol is identical to MySQL, therefore MySQL Workbench, MySQL Cli tools, all tools work with MemSQL out of the box.
I seriously looked at Redis and SQL Server 2016 in-memory DB. Redis was rejected because it isn't really a database. And SQL Server because it can't scale out, only up.
MemSQL was easy to install and do a quick test. Plus, you can just fire up a MemSQL appliance on Azure.
The cool thing about it, compared to other in-memory tools, is that its communications protocol is identical to MySQL, therefore MySQL Workbench, MySQL Cli tools, all tools work with MemSQL out of the box.