⏱ 5 min read A news feed service delivers a ranked, personalized stream of posts to each user. The central design question is delivery […] Read article

⏱ 6 min read A payment dispute resolution service manages the lifecycle from the moment a customer contests a charge through investigation, bank communication, Read article

⏱ 4 min read Overview A calendar and meeting invite service lets users create events, invite attendees, track RSVPs, and synchronize with external calendar Read article

⏱ 5 min read A password manager is security-critical software. Every design decision either exposes user secrets or protects them. The central architectural constraint Read article

⏱ 6 min read The transactional outbox pattern solves one of the most common reliability problems in microservices: how to write to a database Read article

⏱ 7 min read Overview A data anonymization service transforms raw datasets containing personally identifiable information (PII) into privacy-safe versions that can be used Read article

⏱ 6 min read What Is a Distributed Caching Layer? A distributed caching layer sits between your application and its primary data store, serving Read article

⏱ 6 min read A dynamic pricing engine adjusts prices in real time based on demand signals, inventory, and business rules. The design must Read article

⏱ 6 min read A session replay service records a user’s browser interactions and reconstructs them for playback — enabling UX debugging, funnel analysis, Read article

⏱ 5 min read A matchmaking service pairs players into balanced, low-latency game sessions. The design touches skill rating systems, queue management, match formation Read article

⏱ 6 min read A thumbnail generation service converts uploaded images into resized, optimized variants for display at different sizes across web and mobile Read article

⏱ 6 min read A media upload service handles ingesting user files — images, video, audio, documents — reliably and at scale. The design Read article

⏱ 6 min read Overview An audit log service provides an authoritative, tamper-evident record of who did what to which resource and when. It Read article

⏱ 6 min read Problem Statement Design an investment portfolio tracker that stores positions, pulls real-time price feeds, calculates gain/loss, alerts on rebalancing drift, Read article

⏱ 6 min read Problem Statement Design the order book engine for a crypto exchange: handle limit and market orders, match them using price-time Read article