For those who have architected big and/or distributed systems, how did you learn various design techniques? What learning resources helped you the most?
Learning platform architecture and devops at scale is sort of a chicken and egg scenario. You can certainly learn and practice on your own but the best way to get good is get hired by companies that actually practice it.
One piece at a time, every large system is comprised of smaller parts and components. One thing always leads to another. Start small, and build your way up.