Of course, you don't need to know any CS fundamentals to "discover" them and start using them. But if you want to learn the CS behind them and how they operate

Of course, you don't need to know any CS fundamentals to "discover" them and start using them. But if you want to learn the CS behind them and how they operate on a theoretical level, I'd say start with the algorithms that power networking and the internet and then progress up to data structures used by these frameworks to deal with databases, caching etc. I'm not too familiar with any of them except for django so I can't get into that much detail.