System Design (High Level Design, or HLD) interviews are a cornerstone of the software engineering hiring process at top product companies like Google, Meta, Amazon, Microsoft, and Uber. In these rounds you are asked to architect large-scale distributed systems from scratch — covering components such as load balancers, databases, caches, message queues, CDNs, and microservices — while justifying every trade-off you make. Interviewers evaluate your ability to reason about scalability, availability, fault tolerance, and performance under real-world constraints.
Performing well in HLD rounds requires far more than textbook knowledge. You need to practice articulating your thinking out loud, handling follow-up questions, and refining designs iteratively under time pressure. InstaMock's AI mock interviewer simulates exactly that environment: it poses a design problem, probes your decisions with targeted questions, and delivers instant, structured feedback on your architecture choices, scalability strategies, and communication clarity — so you can improve with every session without waiting for a human reviewer.
Our problem set spans the most commonly asked system design topics, including real-time messaging (WhatsApp), video streaming (Netflix, YouTube), ride-hailing (Uber), file storage (Dropbox), e-commerce (Amazon, Airbnb), payment systems, notification services, rate limiters, web crawlers, and more. For each topic that has a dedicated design guide, you can first study the theory — covering architecture diagrams, capacity estimation, and component deep-dives — and then immediately put your knowledge to the test in an AI mock interview session. Track your progress on the leaderboard and see how you rank against other engineers preparing for the same interviews.
Learn to architect a messaging platform like WhatsApp. Master message delivery guarantees, one-to-one and group chat, presence indicators, end-to-end encryption, and handling millions of concurrent connections. Essential WhatsApp system design interview preparation.
Design a large-scale video streaming platform like YouTube. Cover video upload and processing, efficient video serving with CDN, adaptive bitrate streaming, recommendations, and handling billions of video views. Master YouTube system design for interviews.
Build a URL shortening service handling billions of short links. Learn collision detection, encoding schemes, database design for fast lookups, expiration handling, and analytics. Classic system design interview problem covering scalability.
Implement rate limiting algorithms (token bucket, sliding window, leaky bucket). Manage distributed rate limiters across multiple servers, handle edge cases, and prevent DDoS attacks. Common system design interview topic for backend engineers.
Build a scalable notification service handling push notifications, emails, and SMS. Master message queues, retry logic, batch processing, and delivery guarantees. Interview favorite for designing asynchronous, event-driven systems.
Architect Airbnb's booking system. Handle inventory management, search with filters, reservations, payments, and review systems. Learn search optimization, distributed transactions, and managing marketplace complexity in interviews.
Design Amazon's core e-commerce system. Master product catalog with search (Elasticsearch), shopping cart, inventory management, order processing with Saga pattern, flash sales handling, and payment processing. Complex system design interview topic.
Build a cloud storage service like Dropbox. Learn file upload/download optimization, versioning, sharing permissions, conflict resolution, deduplication, and efficient storage. Interview favorite for distributed systems and storage design.
Architect a food delivery platform (Uber Eats, Zomato). Master restaurant discovery with geospatial queries, order management, real-time delivery tracking, payment processing, and handling surge pricing. Complex system design interview.
Build a secure payment processing system. Learn idempotency, transaction management, PCI compliance, fraud detection, reconciliation, and handling failed transactions. Critical system design topic for fintech and e-commerce interviews.
Architect a quick commerce platform (15-30 min delivery). Master inventory at multiple warehouses, real-time delivery tracking, demand forecasting, and managing high throughput during peak hours. Modern system design interview topic.
Build a ticket booking system for concerts, movies, or flights. Handle simultaneous booking attempts, prevent overbooking with pessimistic/optimistic locking, manage reservations, and handle payment failures. Popular system design interview problem.
Design a web crawler that efficiently fetches billions of web pages. Master URL frontier management, politeness constraints, duplicate detection, distributed crawling, and handling failures. Interview topic testing your understanding of distributed systems.