What to Expect and How to Prepare
This is a practical reference for preparing mobile-focused system design interviews, including what to expect, what to practice, and how to stand out.
Unlike traditional system design interviews that focus heavily on backend infrastructure, mobile interviews test how you approach architectures, modularization, and real-world mobile challenges — like turning designs into features, syncing offline data, and handling locally stored data.
Whether you're targeting a senior role or your first mobile interview, this page walks you through:
Read on or go straight to the resources to prepare.
The best interviews feel like collaborative problem-solving, or pair programming. Except you lead the design; the interviewer adds constraints and curveballs — just like real life.
The start of the interview is light, you'll have a short introduction, and will soon move on to the interview phase.
But don’t waste time.
You’ll be presented with a feature or system to design. It's intentionally vague. They’re testing how you clarify, architect, and communicate, not how much you’ve memorized.
You’ll likely face a prompt like:
These often sound deceivingly simple, but they touch on deep topics:
When doing this remotely, it's likely you'll use a browser-based editor, such as CodeSignal or HackerRank.
In person you will likely use your own laptop, a company's laptop, or a company's whiteboard.
You will draw either diagrams, or write (pseudo)code to show which components you need to make a full system to solve the requirements.
Usually you'll use a combination of text, code, and diagrams to explain your thought process.
💡 Tip: You don't need to deliver a perfect program. Remember: You are designing a system, not delivering one! You might leave things unfinished or flawed, and that is completely okay. The goal is to share your thought process and ability to turn vague requirements into a strong design.
Once you present your initial design, there is a big chance the interview will ramp up in difficulty. Interviewers will often throw in follow-up requirements, just like in real life, where specs evolve and teams adapt.
These twists test how well you:
Below you'l find useful articles, videos, and book excerpts to help you prep quickly and think clearly during interviews.
Quick, practical reads to sharpen your system design thinking.
Practical lessons and real chapters from the Mobile System Design book.
For the full strategy, start with the first eight chapters. You’ll learn how to shape vague requirements into strong architectures, implement scalable patterns, learn testing strategies, and how to handle Dependency Injection at scale — no third-party frameworks required.
Prefer watching over reading? These quick videos explore practical ways to think through system design prompts.
The full book package includes a printable Quick Reference Cheat Sheet, real-world prompts, mobile-focused diagrams, and practical strategies to help you prep faster and answer with clarity.
❝It has helped me crack some of the most difficult System Design interviews.
It's even helping in my current role where I'm heading the mobile division.❞
— @_thatabishek
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