Learn to design scalable, reliable systems that handle millions of users. System design interviews test your ability to architect real-world applications, considering tradeoffs, scalability, and best practices.
Core Topics:
Scalability: Load balancing, horizontal vs vertical scaling
Storage: Databases (SQL vs NoSQL), caching (Redis, Memcached)
Reliability: Replication, failover, disaster recovery
Performance: CDNs, caching strategies, database indexing
Common Design Questions:
Design URL shortener (bit.ly)
Design rate limiter
Design Twitter/Instagram feed
Design messaging system (WhatsApp)
Design file storage (Dropbox)
Interview Level: Senior engineers (L5+) at FAANG companies. Requires 3-5+ years experience to tackle effectively.
Preparation: Study system design patterns, understand distributed systems fundamentals, and practice mock interviews.
3 min read “Design Signal” or “design an E2E messenger” is a senior+ mobile-system-design prompt that probes whether you understand modern cryptography, multi-device […] Read article
3 min read “Design a transit app” is a niche but technically rich mobile-system-design prompt. Citymapper, Transit, Moovit, Apple Maps Transit are the Read article
3 min read “Design a travel booking app” combines search at scale, payment, complex itinerary management, and the unforgiving UX of “I am Read article
3 min read “Design a mobile browser” is a senior+ mobile-system-design prompt that probes whether you understand the platform constraints (especially iOS WebKit), Read article
3 min read “Design a mobile video editor” is one of the harder mobile-system-design questions because the stack involves GPU rendering, a non-trivial Read article
3 min read “Design in-app purchases and subscription validation” is the unglamorous mobile-system-design question that pays for many apps. The interview tests whether Read article
3 min read “Design a live sports app” is a senior mobile-system-design prompt that combines real-time data, video streaming, push at scale, and Read article
3 min read “Design an audiobook app” is the audio-only cousin of the music-streaming and podcast prompts. Audible, Libby, Spotify Audiobooks, Apple Books Read article
3 min read “Design a food-delivery app” is the consumer-side mobile-system-design counterpart to the courier-side question. The interviewer wants to see how you Read article
3 min read “Design a camera app” is a senior-level mobile-system-design question that probes whether you understand the capture pipeline, on-device ML for Read article
3 min read “Design a mobile crypto wallet” is a security-heavy mobile-system-design question. The interviewer is testing whether you understand the difference between Read article
3 min read “Design Family Sharing” is a multi-account mobile-system-design question — the interviewer is checking whether you understand identity and authorization across Read article
2 min read Plant care apps (PictureThis, Planta, Greg) and pet care apps (11pets, Pawtrack) seem niche but pop up frequently in mobile Read article
2 min read Read-it-later apps (Pocket, Instapaper, Matter, Readwise Reader) save articles for later consumption — stripped of ads, formatted for reading, available Read article
2 min read Group expense apps (Splitwise, Tricount, SettleUp) sit at the intersection of social and financial. The interview tests whether you understand Read article
