hard Problems
12 problems at hard level.
Design Uber: Ride Matching, Location Tracking and Pricing
Solve the Uber system design interview: real-time location updates, driver matching, geospatial indexing, trip state, pricing, scale, and tradeoffs.
Design a Location-Based Service
Design a location-based service with geospatial indexing (QuadTree/GeoHash), proximity search, real-time location updates, and geofencing.
Design a Food Delivery System
Design a food delivery system (DoorDash/Uber Eats) with three-sided marketplace, order tracking, driver dispatch, and ETA calculation.
Design Google Docs: Real-Time Collaboration and Conflict Resolution
Solve the Google Docs system design interview: real-time editing, operational transform or CRDTs, presence, storage, permissions, and scaling tradeoffs.
Design Google Maps
Design Google Maps with graph routing (Dijkstra/A*), tile rendering, real-time traffic, geocoding, and turn-by-turn navigation.
Design Zoom: WebRTC, SFU, Meetings and Recording Architecture
Solve the Zoom system design interview: WebRTC, SFU media routing, meeting control plane, screen sharing, recording, NAT traversal, and scaling.
Design Dropbox
Design Dropbox with file sync, chunking, deduplication, conflict resolution, and delta sync. Covers the sync protocol and metadata management.
Design Ticket Booking: Seat Holds, Concurrency and Payments
Solve the ticket booking system design interview: seat maps, temporary holds, concurrency control, payment flow, queues, scaling, and tradeoffs.
Design a Web Crawler
Design a distributed web crawler with URL frontier, politeness policies, content deduplication, and distributed coordination.
Design a Code Deployment System: CI/CD, Canary and Rollback
Solve the code deployment system design interview: build pipelines, artifact storage, canary releases, blue-green deploys, rollback, and observability.
Design Cloud Storage (S3)
Design an object storage system like S3 with erasure coding, metadata service, multi-tenancy, and 11 nines of durability.
Design a Distributed Lock Service
Design a distributed lock service with consensus-based locking, fencing tokens, TTLs, and leader election. Covers Chubby/ZooKeeper architecture patterns.