System design problems specific to mobile apps — offline-first sync, battery, location, push notifications, and platform constraints on iOS and Android.
2 min read Receipt-scanning expense apps (Expensify, Zoho Expense, modern fintech wallets) have become routine for business travelers and freelancers. The interview tests […] Read article
2 min read Mobile sleep tracking has gone from gimmick to mainstream — Apple Health, Fitbit, Oura Ring, Whoop, and dozens of dedicated Read article
2 min read Investment-tracking apps (Personal Capital, Wealthfront, Empower, Yodlee-based apps) aggregate accounts across brokerages, banks, and retirement plans. The interview is multidisciplinary: Read article
2 min read Habit-tracking apps (Streaks, Productive, Habitify, Atomic Habits-inspired apps) are simple-looking but reveal interesting system design questions: streak calculation, time-zone sensitivity, Read article
2 min read Travel itinerary apps (TripIt, Hopper, Google Trips legacy) auto-organize a trip from confirmation emails into a unified itinerary. The interview Read article
2 min read Personalized push notifications are an entire engineering discipline. The wrong notification produces uninstalls; the right one produces engagement. Companies like Read article
3 min read Deep linking — the ability to open a specific screen in your app from a URL — is fundamental to Read article
2 min read Mobile loyalty apps (Starbucks, Chipotle, Dunkin) are unusually rich mobile system design topics. They combine payment processing, loyalty points, mobile Read article
2 min read Crash reporting (Crashlytics, Sentry, Bugsnag) is a system design topic that touches mobile SDK design, server-side processing of millions of Read article
2 min read The Uber driver app is a different beast from the rider app. It runs all day, must survive on cellular, Read article
2 min read Voice assistants (Siri, Google Assistant, Alexa) are deceptively complex mobile system design topics. Always-listening for a wake word, on-device automatic Read article
2 min read Onboarding is one of the highest-leverage UI flows. Every percentage point of drop-off is real users who never become customers. Read article
2 min read Modern mobile translation apps (Google Translate, Apple Translate) increasingly run inference on-device. The interview tests whether you understand the tradeoffs Read article
2 min read Live audio rooms (Clubhouse, Twitter Spaces, Discord Stage Channels) are an interesting mobile system design topic. They sit between video Read article
2 min read QR scanners are a deceptively rich mobile system design problem. Camera capture in real time, edge case handling (low light, Read article
