In my experience, MySQL is not an acceptable backend for a triplestore. You should consider using any one of the many dedicated triple stores, any of them will probably outperform MySQL because they do not have the impedance mismatch of triple to store triples/quads into a relational store; they're using native storage.
There is no production ready solution based on Redis that I'm aware of. A quick google turned up a couple projects that seem to be related, but they may not meet your requirements.