Loading…
Compiling brilliance
Did you know? An LRU cache is a HashMap + a doubly-linked list → O(1) get & put.
Compiling brilliance
Did you know? An LRU cache is a HashMap + a doubly-linked list → O(1) get & put.
the five-year mile
Master the HLD, LLD, and CS fundamentals that make or break interviews. Learn through first-principles reasoning and complete, production-ready code.
Understand the why. Don’t just memorize the what.
Dive into full, file-by-file implementations using our integrated IDE viewer. Because the best way to learn is by reading real code.
// SYSTEM DESIGN// Q: Design an API rate limiter —// N requests per window, per client,// O(1) to check and thread-safe. Every article moves you one marker further down the road.
Year 1
Ships features that work
Year 2
Reads big codebases fast
Year 3
Owns a service end to end
Year 4
Designs for scale & failure
Year 5
Reasons from first principles
Prefer a guided week? Take a course
All-in-one interview prep — the right topics in the right order, with tested code and hand-drawn diagrams. Day 1 is free.
Fresh from the notebook
A diagram-first guide to the array and dynamic array data structure: O(1) random access, why append is amortized O(1) via doubling, time complexity, and interview questions.
Balanced search trees explained: AVL and red-black, the self-balancing binary search tree data structure that guarantees O(log n). Rotations, time complexity, and interview questions.
A diagram-first guide to Big-O notation and time complexity analysis: the growth classes from O(1) to O(n!), reading complexity off code, space complexity, amortized analysis, and interview prep.
Start with the two that interviews lead with