System Design Problems

Design a real-time leaderboard system for a multiplayer online game with millions of concurrent players. The system should handle score updates, rankings, and friend comparisons.

Design a graph database system optimized for social network queries and recommendation engines.

Design an automated content moderation system for a social media platform using ML and human review.

Design an event sourcing architecture for a financial application requiring complete audit trails.

Design a feature flag management system for controlled rollouts, A/B testing, and kill switches.

Design an API gateway that handles authentication, rate limiting, routing, and request transformation for microservices.

Design a metrics collection and monitoring system like Datadog or Prometheus handling millions of time-series data points.

Design the core matching algorithm for a ride-sharing service that optimizes driver-rider pairing.

Design a distributed web crawler that can index billions of web pages efficiently while being polite to websites.

Design a multi-channel notification system supporting push notifications, email, SMS, and in-app messages at scale.

Design a real-time collaborative editing system supporting multiple simultaneous editors with conflict resolution.

Design a distributed lock service like Apache ZooKeeper or etcd for coordinating distributed systems.

Design a food delivery platform like DoorDash or Uber Eats handling restaurant listings, order management, and real-time delivery tracking.

Design a globally distributed DNS system like Cloudflare or Route 53 that handles billions of queries per day.

Design a real-time fraud detection system for financial transactions that can identify suspicious patterns with minimal false positives.

Design the video processing pipeline that encodes uploaded content into multiple formats and resolutions for streaming.

Design a distributed task scheduler like Apache Airflow or Temporal that can handle millions of scheduled jobs with dependencies.

Design a calendar application supporting event scheduling, recurring events, shared calendars, and meeting room booking.

Design a high-frequency stock trading platform handling order matching, real-time price updates, and trade execution with microsecond latency.

Design a real-time messaging platform like Slack or Discord supporting channels, direct messages, file sharing, and presence indicators.

Design a video sharing and streaming platform supporting upload, transcoding, streaming, recommendations, comments, and likes.

Design a ride-sharing application matching drivers with passengers, handling real-time location tracking, fare calculation, and payments.

Design a microblogging platform where users post tweets, follow others, like, retweet, and view a timeline feed.

Design a real-time messaging application like WhatsApp supporting 1-on-1 chat, group chat, media sharing, and message delivery receipts.

Design a global video streaming platform that serves millions of concurrent users with personalized recommendations and adaptive bitrate streaming.

Design a system like bit.ly that converts long URLs into short, memorable links. The system should handle billions of URLs with high availability and low latency.

Design a photo-sharing social media platform like Instagram. Users can upload photos, follow others, like posts, and view a personalized feed.

Design a strategy to migrate a monolithic system serving 10M users to microservices with zero downtime.

Design a reliability program using SLOs (Service Level Objectives) to balance feature velocity with system stability.

Design an organizational structure for scaling an engineering team from 20 to 200 engineers while maintaining velocity.

As an Engineering Manager, design a system to identify, prioritize, and systematically address technical debt across your organization.

Design an internal developer platform strategy to improve developer productivity and standardize infrastructure across 50+ engineering teams.

As a Software Architect, design a framework for making and documenting architectural decisions across multiple teams.

Design an incident management process and supporting systems for a 24/7 operation with 99.99% uptime requirements.

Design a mapping and navigation service like Google Maps with features like map rendering, directions, and real-time traffic.

Design a payment processing system like Stripe or PayPal handling transactions, refunds, and fraud detection.

Design a distributed rate limiting system to protect APIs from abuse and ensure fair usage.

Design a distributed caching system like Redis or Memcached that can handle millions of requests per second.

Design a real-time collaborative document editing system like Google Docs supporting multiple concurrent editors.

Design a photo-sharing social network like Instagram with features like posting photos, following users, and a personalized feed.

Design a microblogging platform like Twitter with features like posting tweets, following users, timeline, and trending topics.

Design a ride-sharing application like Uber supporting real-time driver matching, location tracking, and fare calculation.

Design a video streaming platform like Netflix or YouTube supporting video upload, transcoding, and adaptive streaming.

Design a real-time messaging application like WhatsApp supporting 1:1 chat, group chat, media sharing, and delivery receipts.

Design a URL shortening service like bit.ly or TinyURL. The system should generate short URLs from long ones and redirect users.

Compare horizontal scaling (scaling out) vs vertical scaling (scaling up). What are the trade-offs?

When should you choose microservices over a monolithic architecture? What are the trade-offs?

Explain different database sharding strategies and when to use each.

Explain the CAP theorem and its implications for distributed system design.

Explain the differences between an API Gateway and a Load Balancer. When would you use each?