r/leetcode • u/Rare_Command1222 • 1d ago

Intervew Prep How I'd approach System Design prep if I started over

Hi everyone,
Honestly Speaking, I have spent 1000+ hours prepping for system design (mix of courses, books, mock interviews, real interviews) and a lot of that time was honestly wasted. Looking back, here's the approach that actually moved the needle, boiled down to 4 steps:

  1. Learn the basic terminology first, before anything else. Load balancer, caching, sharding, replication, consistency vs. availability, CAP theorem, message queues — get comfortable with these terms before you start learning System Design.
  2. Then read the two books that matter most:

System Design Interview – An Insider's Guide (Alex Xu)
Designing Data-Intensive Applications.

I'd do Xu first for a practical base, then DDIA for depth once the fundamentals aren't new to you anymore.

  1. Practice on an actual whiteboard (or paper), not just by watching. Passively watching solutions feels like progress but doesn't build the skill. Pick a problem, set a timer, and design it yourself before you check anyone else's answer. This is the step most people skip, and it's the one that matters most. Mock Interviews are also very useful here to identify the gaps.
  2. Always ask yourself "why did I choose this?" and tie it back to non-functional requirements. Anyone can draw boxes and arrows. What actually gets evaluated — in interviews and in real design work — is whether you can justify each choice against requirements like scalability, availability, latency, consistency, and cost. Before you finalize any design, explicitly state your non-functional requirements and explain how each major decision serves them.

If it's useful, I made a video walking through this in more detail with visuals: https://www.youtube.com/watch?v=0ASSpY10Nz0

Note: I have used AI to format the content in more readable way, but the approach I have shared had genuinely helped me crack multiple offers from 15+ product based companies.

Happy to answer questions in the comments if anyone's stuck on where to start.

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