Cap'n Proto is an insanely fast data interchange format and
capability-based RPC system. Think JSON, except binary. Or think
Protocol Buffers, except faster. In fact, in benchmarks, Cap'n Proto
is INFINITY TIMES faster than Protocol Buffers.

This benchmark is, of course, unfair. It is only measuring the time
to encode and decode a message in memory. Cap'n Proto gets a perfect
score because there is no encoding/decoding step. The Cap'n Proto
encoding is appropriate both as a data interchange format and an
in-memory representation, so once your structure is built, you can
simply write the bytes straight out to disk!