Not sure if this is what you are looking for but I found this paper useful on architecting databases. I read it as a complement to the CMU videos. https://dsf.berkeley.edu/papers/fntdb07-architecture.pdf

Otherwise there is surprisingly a lack of information about architecting databases online and you have to go to the source code of SQLite and PostgreSQL. I suspect this is because databases are some of the most complex systems in computer science and involve many trade secrets.

On-line docs describing the design and internal operation of SQLite include: https://sqlite.org/arch.html https://sqlite.org/optoverview.html https://sqlite.org/opcode.html https://sqlite.org/queryplanner.html https://sqlite.org/atomiccommit.html

Inspired by this post, I started yet another: https://sqlite.org/draft/howitworks.html