Ask HN: How do I study distributed sytems?

I'm at the juncture of my career where I want to focus more on Distributed Systems and specialize more in it. Short of reading seminal papers, understanding existing data systems like Spark, Kafka etc., how do I gain more working knowledge so as to improve my implementation skills of such a system.

While I haven't really worked on a major project that explores core problems, I'd like to spend the next year or two learning more about it.

Looking forward to learning from the pioneers in this field who have implemented many such systems.