The interview prep resource I wish existed.
Mobile System Design is a free, depth-first Android interview prep resource built for engineers targeting Staff and Principal roles. It covers every topic that comes up in real system design interviews — with the level of detail you actually need to pass them.
13
Deep-dive chapters
31
Real post-mortems
26
Behavioral scenarios
25
Requirements Lab problems
25
Code Review exercises
25
Staff+ Mindset challenges
Why I built this
I'm Sahitya Pasnoor, an Android engineer who spent months preparing for Staff-level system design interviews. Most resources I found were either too generic (aimed at backend engineers), too shallow (surface-level Compose tutorials), or behind a paywall that didn't justify the depth.
I wanted a resource that treated Android engineers as the domain experts they are — covering the real tradeoffs between WorkManager and Foreground Services, the memory model behind Bitmap handling, the difference between Staff and Principal thinking in a real incident. So I built it.
Everything here is free. No paywalls, no email required, no ads. Just the content.
What's inside
Study Guide
13 chapters covering App Architecture, Compose, Networking, Offline-First, Concurrency, Security, Performance, Engineering with AI Agents, and more — written at Staff/Principal depth, not tutorial level.
Autopsy Lab
31 real Android post-mortems (Snapchat, Discord, Spotify, Instagram, TikTok, AI-era cases…) dissected as case studies. Identify the architectural failure before the verdict is revealed.
Behavioral Prep
26 scenarios drawn from real Staff and Principal interview patterns, including AI-era leadership challenges. Progressive disclosure reveals how Senior, Staff, and Principal engineers frame the same situation differently.
Requirements Lab
25 AI-powered mock interviews. Practice gathering requirements under pressure — the interviewer adapts to your questions in real time.
Code Review Lab
25 real broken Kotlin code samples, including AI-generated bug patterns. Identify the antipatterns, submit your diagnosis, then see the fixed version and the lesson.
Staff+ Mindset Challenges
25 real work scenarios showing how Senior, Staff, and Principal engineers approach the same situation differently — architecture decisions, team conflicts, AI tooling boundaries, and more.
Audio Lessons
Every chapter topic narrated. Study on your commute, during a run, or anywhere without a screen.
Spaced Repetition
Wrong quiz answers are automatically scheduled for review using an SM-2 algorithm. The app surfaces your weakest areas right before you forget them.
About the author
Sahitya Pasnoor is an Android engineer with experience at multiple product companies. His focus areas are architecture, performance, and developer experience on Android.
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