Practise system design interviews, don't just read about them

Prepd is where software engineers practise system design (HLD), low-level design (LLD) and AI/ML systems design. Questions are split into the phases a real interview moves through — requirements, estimation, API design, high-level architecture, deep dive — and you answer each one in writing or on a diagram and get told what an interviewer would push back on.

Three tracks

• System Design (HLD): distributed systems, caching, load balancing, message queues, database sharding, consistency and the CAP tradeoffs.
• Low Level Design (LLD): object-oriented design, SOLID, design patterns, class hierarchies, API contracts and concurrency.
• AI/ML Systems: feature stores, model serving, A/B testing, recommendation engines, RAG pipelines and MLOps.

AI mock interviews

A conversational interviewer that asks follow-ups based on how you answered, scores you out of 100 and hands back a scorecard naming your weak moments. Voice mode included.

Start free

• Design Lab — free interactive games for estimation and consistent hashing, no account needed.
• Free guides — practical write-ups on each interview phase, each ending in drills.
• Learning path — system design concept by concept, first topic free.
• Exercise library — browse every question by track and difficulty.
• Questions by company — what was actually asked, grouped by employer.