Apple iOS Engineer Interview Guide

The first round of the Apple iOS Engineer interview process is a video call with the hiring manager, which is typically a straightforward round that includes general character-based questions and a discussion of your past experiences. The hiring manager will use this opportunity to assess your understanding of Apple's development frameworks and your experience with iOS application development or app development in general. It gives them a better sense of your personality, communication skills, and your motivation to join the company.

During this round of iOS Engineer Interview process at Apple, you can expect questions such as:

1. Tell me about yourself.

2. Can you walk me through a project you worked on that showcased your knowledge and experience in iOS development?

3. Have you worked with any cloud platforms such as AWS or Firebase for backend integration?

4. How do you approach debugging and troubleshooting issues in your iOS applications?

This interview is quite similar to the one which occurs for the Meta iOS Engineer.

Make sure to come prepared with examples of your projects that demonstrate your interest and understanding of the Apple operating system.

The second round is a technical phone screen that typically lasts for one hour. During this time, the interviewer will test your technical skills and your ability to solve problems. The standard technical interview starts with behavioral questions, followed by standard LeetCode questions with various explanatory follow-up questions in between.

Here are some examples of the types of questions you may be asked:

1. Can you explain the difference between a stack and a queue, and when you might use each of them in an iOS application?

2. Given an array of integers, write a function that returns the indices of two numbers that add up to a specific target value.

3. Explain your understanding of the Model-View-Controller (MVC) design pattern, and how it is used in iOS development.

4. What is TCSH?

Stick with LeetCode practice and review your knowledge of iOS development frameworks, data structures, algorithms, and software development processes—you should be well-prepared for the technical phone screen round!

The third and final round in the Apple iOS Engineer Interview process is a long interview conducted onsite (or virtually) and typically lasts about six hours. You meet with several interviewers who test your technical knowledge, your coding and problem-solving abilities, and your ability to architect large-scale systems, as well as work collaboratively with a team.

This interview is quite similar to the one which occurs for the Tinder iOS Engineer.

The algorithm/data structure portion of the onsite round is designed to test your problem-solving skills and technical expertise. This round typically lasts 45 minutes and includes verbal questions about iOS development concepts such as threading, as well as coding questions in Swift or Objective-C.

During this round, the interviewers may ask you to write code on a whiteboard or in an online editor to solve coding problems related to data structures or algorithms (make sure to explain your thought process while solving).

Some examples of questions are:

1. Write a binary tree DFS function in Swift.

2. Explain the difference between a stack and a queue data structure.

3. Given an array of integers, write a function to find the two numbers that add up to a given target.

4. How would you handle race conditions when dealing with threads in an iOS application?

Make sure to go well-prepared with your knowledge of common data structures and algorithms used in iOS development, and practice solving coding problems using online resources such as LeetCode or HackerRank. Additionally, brush up on your knowledge of Swift or Objective-C programming languages.

The behavioural portion of the onsite round will test your ability to work collaboratively with a team and your communication skills. The interviewers may ask you about your experience working on tech projects, your approach to problem-solving in the context of iOS development, and how you handle conflicts or challenges in a team setting.

Examples of behavioral questions you may be asked in an Apple iOS Engineer interview include:

1. Tell me about a time when you had to solve a difficult problem in an iOS application you were working on.

2. How do you approach working with a team of developers and designers to create a user-friendly iOS application?

3. Have you ever had to make changes to an iOS application based on user feedback? How did you approach this situation?

Think ahead about your past experiences working on iOS projects and demonstrate how you have handled challenges or team conflicts previously. Be specific and provide concrete examples from your past experiences. This will demonstrate your ability to apply your skills and experience to real-world situations.

Finally, during the system design portion of the onsite round, you will be asked to design a system that meets certain requirements. This may include designing an iOS application architecture, discussing how to optimize application performance, or explaining how to ensure application security.

It’s important to note - the iOS System Design interview is a bit different from traditional “backend-focused” system design. The interviews you’ll face will be much more app-focused than back-end-focused so it’s worth investing into preparing for them.

Your interviewer is trying to understand your ability to solve a complicated iOS engineering design problem. Or in other words - can you architect a high-level solution to a problem that has multiple concepts and components? 

Ideally, you’ll cover a range of topics that are going to prove relevant in the actual job - the view layer, the networking, storage, cache, etc. The 3 things they are specifically looking for are:

1. Technical skills - reflected through your knowledge of different technologies, awareness of side-offs and system interactions, the tradeoffs involved, and the ability to build something that is flexible and scales effectively.
2. Structure and approach - do you scope the problem? how do you clarify requirements or constraints? Are you familiar with MVVM and MVC, and can you apply the principles. Do you actually understand the remit of the business problem, and how this leads to the use cases you’re solving for? Did you drive the discussion or were you passively reacting to what your interviewer moved you to?
3. Communication and collaboration - how do you interact with your interviewer, are you able to explain your thinking and go into the right level of detail, do you have a partnership approach to solving this problem? Do you just make assumptions or do you discuss these with your interviewer?

We have 5 tips - this is the most critical part of this guide

1. Scope and clarify. This is maybe the most critical one since these questions are super broad and you want to narrow definitions down into something you can actually attack in the 40min or so you have. 
2. Have a structure and methodical approach. My general recommendation is to split things into discrete layers starting from the View, Controller, Network, Storage, Cache since this is how you’d design a system in real life. 
3. Which brings me to my third tip. Watch out for hints. Let me give an example, maybe you’re designing some kind of calendar element, and your interviewer asks “Are you sure you’d just store a single timestamp for this event” - this is an explicit hint that you might be missing something, maybe you should be storing a StartTime and an EndTime, or maybe there’s some complexity related to timezones or something. Use this as an opportunity to either pivot, or clarify, or explain your thinking. 
4. Which neatly flows over into my 4th tip. Think out loud. You’re solving a problem, and it’s super useful for your interviewer to know how you’re approaching it - and even more so for you, since they can “course correct” you if you’re going down the wrong tangent, or a line of thinking they’re not interested in.
5. Finally - practice. Practice with professionals. Prepfully has 18 iOS Engineers who help candidates with mocks. They’ve collectively helped over 500 candidates already, in the last couple of months - which means they’ve got great insight into the common mistakes to avoid, as well as advice on how to improve.

Examples of system design questions you may be asked in an Apple iOS Engineer interview include:

1. How would you design a scalable iOS application architecture that can handle a large number of users?

2. Can you explain how you would optimize the iOS application for performance, and what tools you would use to measure performance?

3. What security best practices would you follow when developing an iOS application, and how would you ensure that the application is secure within the Apple ecosystem?