[wowmsi]

I would recommend "Architecture of a Database System" by Joe Hellerstein, Micheal Stonebraker, and James Hamilton [0] as a start if you want formal perspective without getting too much into theory.

[0] http://db.cs.berkeley.edu/papers/fntdb07-architecture.pdf

[jbergens]

As a sidenote, Michael Stonebreaker himself is nowdays building VoltDb which is a memory-db that he thinks is much more evolved than relational systems. I havn't used it but it looks interesting. I did try OrigoDb which is an open source .NET based memory db and it worked great for my needs and the queries are really fast.

[bballard]

(I work at VoltDB)

VoltDB is easy to try. There is a free 30-day trial available on voltdb.com, and a docker-based demo (http://voltdb.com/voltdb-demo).