Design It — system design practice
7 scaffolded parts per problem: requirements, APIs & data model, architecture, core mechanism, extended features, security, and scalability tradeoffs — each graded against a rubric, not a vibe check. 2 problems, 2 free, no card required.
Design a URL Shortener
Design a service like bit.ly — takes a long URL, returns a short code that redirects back to it.
Design a Rate Limiter
Design a rate limiter that a shared API gateway calls before forwarding each request, protecting downstream services from abusive or runaway clients.
System design interview practice, answered
A system design interview asks you to scope, diagram, and defend an architecture under constraints an interviewer keeps tightening. Senior Loop's Design It problems are staged the same way a real round is run — a fixed 7-part scaffold covering requirements, APIs & data model, architecture, core mechanism, extended features, security, and scalability tradeoffs — each part graded against a rubric, not a vibe check.
What is a system design (HLD) interview?+−
You're given an open-ended prompt — design a rate limiter, a URL shortener — and asked to scope requirements, sketch an architecture, and defend tradeoffs as the interviewer pushes on scale and failure modes.
How is this different from LLD (Build It)?+−
HLD is services, data stores, and scale at the architecture level. LLD is one level down — the actual classes and interfaces that make a single component correct. Design It practices the former; Build It practices the latter.
How does grading work without a human interviewer?+−
Each of the 7 parts has a rubric — specific points a senior answer should cover, plus (for the architecture part) the components and connections a correct design needs. The AI grader checks your submission against that rubric, not against a vague quality heuristic.