Memcache

> "Simplicity is prerequisite for reliability." [Edsger W. Dijkstra](https://www.cs.utexas.edu/users/EWD/transcriptions/EWD04xx/EWD498.html) As our experience grows, we learn from past mistakes and discover what's truly important in reliable systems. When designing systems, simplicity is an often heard mantra, but it isn't getting applied nearly as much as spoken of. I'm guilty of this too. I think it's mainly because engineers love to, well, engineer :) and will naturally try to [outsmart problems by throwing more tech at it](https://teddziuba.com/2010/12/the-3-basic-tools-of-systems-engineering.html).

Don't know Redis? Think Memcache, with support for for lists, and disk-based storage. You can use Redis as a database, queue, cache server or all of those combined. Let's see how you can use this power in your PHP apps.

In PHP, sessions can keep track of authenticated in users. They are an essential building block in today's websites with big communities and a lot of user activity. Without sessions, everyone would be an anonymous visitor.