Among other things, Drew is the primary designer and implementor of HHVM's virtual instruction set architecture and Hack's Collections framework, and he was a core contributor to HHVM's JIT compiler in the early days of the project. Before Facebook, Drew was at Microsoft where he worked on improving the performance of Microsoft's runtime and JIT compiler for .NET languages (C#, VB.NET, F#, and more) known as the Common Language Runtime. Drew enjoys designing and optimizing complex low-level systems and been coding in C++ for over 10 years.