I always enjoy these insights into how they are building Cockroach DB.
Could you imagine having this level of detail laid out during the development of postgres or mysql?
design documents within the repo itself (under docs/RFCs [0]) actually do well to capture some of the past implementation details/rationale and future directions CockroachDB is planning to take. in my (very biased) opinion they've gone out of their way to keep everything as transparent as possible.