Pilosa, https://github.com/pilosa/pilosa https://github.com/pilosa/pilosa which is mentioned, is actually open source, and a relatively readable Go codebase if

Pilosa, https://github.com/pilosa/pilosa https://github.com/pilosa/pilosa which is mentioned, is actually open source, and a relatively readable Go codebase if anyone is interested in what "an entire data engine on top of bit-vectors" looks like.