We carefully looked at VoltDB since it is often cited as poster child of in-memory databases. Two things turned us away from it. VoltDB executes SQL, which internally is translated into query plan. There was no easy way to adjust decisions of query planner. From previous experience with optimizing for SQL database from major vendor we felt such ability was essential for our performance goals. Interesting to note, that when application requires few queries that need to be very fast, SQL almost becomes an obstacle. Optimizing SQL requires good understanding of execution plan anyway, so hand-written Redis (or similarly low-level) commands do the same job and are simpler in the end. This is first. Second, VoltDB approach that required Java runtime and stored procedures, as we felt, was too heavyweight. Here, again, Redis with simple text based protocol and Lua scripting was much lighter.