Best system design learning resource?

Some of the youtube sources I found helpful to learn about system design: Gaurav Sen/harvard scalability lecture/Jackson Gabbard Also, there is a guy named abrar who has videos of mock interviews with bunch of real life engineers (interviewing.io)

Tech dummies narendra

If you’re looking to do a mock interview, targeting YouTube, have you looked at sites like Gainlo.co or PracticeCodingInterview.com? Both of those sites also had good blogs IIRC.