Josh Prewer

5 Tips for Acing iOS System Design Interviews

Landing a job as an iOS developer can be a highly competitive process. One of the key steps in this journey is acing the system design and whiteboarding interviews. These interviews evaluate a candidate's ability to design, architect, and communicate complex technical solutions at a higher level. To help you succeed, I’ve compiled five essential tips for navigating iOS system design interviews.

Understand the Problem

Before diving into your solution, breathe. You’ll likely have been given an ambiguous problem. It might be a few screenshots and the interviewer has asked “how would you build this app?”.

Understand what is being asked from you. Asking refinement questions can help you narrow the scope of the problem and lead to a better solution. Some good questions to ask are:

  • What are the functional and non-functional requirements of the app?
  • What does the response from the Backend look like
  • Does it need to support offline mode?
  • Will users need to have an account

A good solution will firstly solve the problem. It’s very hard to solve the problem if you don’t understand the problem.

Practice Problem Solving

Popular iOS system design interview topics include:

  • Networking and API integration
  • Data persistence and storage
  • UI design and layout
  • Testing strategies
  • Security requirements

You’ll likely be working on a problem that covers a number of these topics. Work through sample problems, and practice explaining your thought process out loud. This will not only reinforce your technical knowledge but also improve your communication skills.

Brush Up on Architectural Patterns

Familiarise yourself with popular architectural patterns used in iOS development, such as:

  • Model-View-Controller (MVC)
  • Model-View-ViewModel (MVVM)
  • The Composable Architecture (TCA)

Each pattern has its strengths and weaknesses. Interviewers often aren’t looking for one architecture over another. Use any you are comfortable with and is appropriate for the problem. Understanding SOLID principles can help guide your solution better than trying to brute force everything to follow VIPER.

Master Whiteboarding Techniques

Effective whiteboarding is crucial for conveying your thoughts clearly and concisely. Here are a few tips to improve your whiteboarding skills:

  • Start with an outline: Before diving into details, sketch a high-level overview of the system. This helps you organize your thoughts and gives the interviewer a clear picture of your approach.
  • Use clear and concise labels: Label components, classes, and functions with meaningful names that are easy to understand.
  • Write legibly: Make sure your writing is large and clear enough to be read from a distance.
  • Engage the interviewer: Encourage questions and feedback throughout the process. This helps ensure that both you and the interviewer are on the same page.

Showcase Soft Skills

While technical prowess is essential, soft skills are equally important. Here are a few soft skills to highlight during your interview:

  • Communication: Clearly articulate your thought process and design choices.
  • Collaboration: Work well with the interviewer, demonstrating your ability to be a team player.
  • Adaptability: Be open to feedback and show a willingness to adjust your design as needed.
  • Problem-solving: Approach problems methodically, breaking them down into manageable pieces.


Acing an iOS system design interview requires a combination of technical knowledge, problem-solving skills, and effective communication. By following these five tips, you'll be well-prepared to showcase your expertise and land that coveted iOS developer role.

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