Month-by-month from fundamentals to interview-ready. Free starters first; Pro lessons marked. Every step links to something you can run, not just read.
Prefer curated sequences? See learning paths or jump to another track below.
Get fluent in the building blocks, and when to reach for each.
Where senior candidates separate: what happens when the network splits.
Stop reading, start designing. Reproduce the classics, then get scored.
Free systems to design against
Also useful
Prove it cold
Draw an architecture and have it scored on scalability, reliability, performance, and security.
Interviews probe whether you've run things in production.
Designing under a 45-minute clock is a different skill. Practice it.
Senior interviews test how you think, not just what you know.
Can you break down an ambiguous prompt, state your assumptions, and defend a decision when challenged? Practice narrating your reasoning out loud on every system you study.
Practice out loud on these
The smallest real system, end to end. Hit play and watch a request flow through it. Free, no account needed.