Clean Architecture (https://www.amazon.com/dp/0134494164) - Uncle Bob has been talking about this for years, but it's a really good exploration of how to build systems.
Turning the Database Inside Out is a talk that really made Apache Kafka and stream processing click with me. https://www.confluent.io/blog/turning-the-database-inside-ou...
Going through and implementing the Raft algorithm was also very formative for me - it's the first time I really started to grok the challenges with building large scale distributed systems. https://raft.github.io/
And to add a paper to the list to not totally go off topic - Birrell's paper "An Introduction to Programming with Threads" I thought was a very useful read - in part for the historical context, but he also breaks down many fundamental concepts that will look very familiar to the modern reader (it was written nearly 30 years ago).
It's also very readable. https://birrell.org/andrew/papers/035-Threads.pdf