Ask HN: What are some ways to learn system design/architecture for a recent grad?

I am a recent grad and I want to learn more about how to design big systems. I read engineering blogs by companies often, although most times I have trouble getting the big picture (the most recent one being understanding how Docker fits into the big picture). I guess it starts with getting to know the architecture of the product I work on, but the product is rather a small one with a simple design.

How should I go about understanding system design and eventually designing big systems? I'd love to hear some of your suggestions. Thanks in advance!