I haven't had a chance to look through it in-depth yet, but this looks pretty interesting: https://github.com/donnemartin/system-design-primer
As far as things that have had an important impact in my learning path, I do have a few Ruby books I really like (the key here is to get your hands dirty with code as you read along):
I think reading about (and looking at the code) for things you use and trying to understand how they work under the hood has been super useful: http://aosabook.org/en/index.html
Having smart people around to learn from is extremely helpful too.
Happy to chat more if you'd like. Just drop me a line: connor[at]opendoor[dot]com
Check out Pat Shaughnessy's Ruby Under a Microscope .
It gives a nice overview of the internals of MRI. It doesn't cover a who lot of the C code, but references plenty of it and where it can be found in the source code of MRI. Grab the book, the source for MRI, and do some digging.
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