Mobile System Design

⏱ 5 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

⏱ 5 min read The interview is multidisciplinary — but first, some context: mobile sleep tracking has gone from gimmick to mainstream — Apple Read article

⏱ 6 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

⏱ 4 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

⏱ 5 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

⏱ 6 min read Personalized push notifications are an entire engineering discipline. The wrong notification produces uninstalls; the right one produces engagement. Companies like Read article

⏱ 4 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

⏱ 3 min read Deep linking — the ability to open a specific screen in your app from a URL — is fundamental to Read article

⏱ 5 min read Mobile loyalty apps (Starbucks, Chipotle, Dunkin) are unusually rich mobile system design topics. They combine payment processing, loyalty points, mobile Read article

⏱ 5 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

⏱ 6 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 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 Designing a Kindle-style mobile reading app is a layered system design problem. Format rendering, position sync across devices, offline downloads, Read article

⏱ 5 min read Mobile news apps (Apple News, Google News, Flipboard, NYT app) sit at an unusual intersection of feed personalization, time-sensitive push Read article

⏱ 4 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