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
Rubyists are a clever bunch, if you find yourself writing the same code over and over again, chances are somebody's already figured out how to refactor it appropriately, tucking away the details behind an intention-revealing module.
A better way to refactor code is in using Ruby's built-in metaprogramming abilities. Metaprogramming Ruby is the best book to show you how.
It focuses on modern Rubies, so it talks about Module#prepend and such. Nice to keep moving forwards.
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