iOS Engineer Interview

To kick things off, you'll likely have a chat with the hiring manager or recruiter, or sometimes both. The call often starts with a brief introduction from both sides; the hiring manager might introduce themselves and their role within the company, and you'll have the opportunity to briefly introduce yourself. This interview is generally a relaxed and informal conversation—the goal here is to understand you better. Expect a similar approach in interviews for roles such as Amazon Android Engineer, where the initial discussions often focus on getting to know the candidate's background and fit for the role.

Beyond that, expect some basic iOS questions – Core Data, UIKit, App Store submission process, you know the drill. They might dig into your experience with iOS frameworks, tools, and best practices. If you have a second phone screen with an HR, they'll toss in some character-based questions and circle back to your tech skills in iOS.

These interviews are usually not too challenging to pass. Ensure you have a concise elevator pitch, have reviewed iOS fundamentals & your previous work experiences, and most importantly, have a compelling answer for why you're interested in joining that particular company. 

Be sure to discuss your relevant experiences and tie them with the said company's values.

This is a more in-depth call where you speak with an Engineer from Tinder who will likely ask you a bunch of coding and technical questions. The aim is to evaluate your technical and problem-solving abilities related to iOS development. 

The contents of the interview vary for different companies. For instance, Google places significant emphasis on Swift, even if your prior experience is primarily in Objective-C. The reason for this is to assess your ability to quickly adapt to new technologies and still deliver a high-quality project—which is a must-have skill at Google.

At Meta, the bulk of the technical screen is dedicated to coding problems. One thing is common for all iOS engineer tech screens: the coding problems aren't typically iOS-specific—and instead tend to focus heavily on computer science fundamentals. They revolve around basic data structures and algorithms. You can also expect theoretical questions like "Frames vs Bounds?" or "what is MVVM-bindings?”

A great way to prepare for the technical phone interview as an iOS Engineer is to practice with mock interviews, especially with experienced iOS Engineers. You can find such experts from top companies like Google, Meta, Tinder on platforms like Prepfully, where you can book 1:1 sessions directly with them. For instance, you can check out the Meta iOS Engineer Interview Guide for targeted preparation.

During the onsite interview, you typically have 4 or 5 interviews over the course of the day. These will be distributed across 4 different types of interviews: iOS Knowledge Interview, Coding Interview, iOS Design Interview, and Behavioral Interview.

• iOS Knowledge Interview: These are often based on practical scenarios you might encounter in your day-to-day work. Expect questions related to iOS development, such as how to use essential APIs, how memory management works in iOS, and so on. 
• Coding Rounds: These typically focus on evaluating your problem-solving skills and understanding of fundamental concepts in context to iOS app development. You may be given multiple technical questions which revolve around analyzing algorithmic complexity and applying data structures effectively. You will be asked to write code on a whiteboard and explain your solution. So, brush up on essential data structures like arrays, linked lists, stacks, queues, and trees. Understand their properties, operations, and time/space complexities. Familiarize yourself with common algorithms like sorting, searching, and graph traversal. Practice implementing these data structures and algorithms in Swift. Some companies also ask you to solve domain-specific problems related to iOS development— be prepared for those as well. For broader coding and problem-solving insights, you might look into roles like Amazon QA Engineer where coding challenges are also a key component.
• iOS Design: This round is typically present if you're interviewing for a senior-level position. You won't be expected to write code for this, but you'll need to design a reasonably complex system.  For instance, “design a system for a real-time chat application on iOS.” It’s important to note - the iOS Design interview is a bit different from traditional “backend focused” system design. The interview 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. Have a structure and methodical approach. Our 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. This approach aligns with design practices for other roles, such as Google Thermal Engineer or Amazon Business Intelligence Engineer, where design and architecture are critical.
• Behavioral Round: This is where they get to know you better as a candidate. They may inquire about your previous experiences, your problem-solving approach within the realm of iOS development, and evaluate your communication abilities. To ace this round, it's important to connect your answers to past experiences and emphasize on the values & culture of the company you’re applying to. Provide specific, concrete examples of times you've displayed excellent collaboration skills, communication skills, etc—essentially traits that company’s value in iOS engineers. For a similar approach, consider how Amazon Business Analyst and Meta Production Engineer roles emphasize cultural fit and communication.

Preparation is key here, for both the design as well as coding rounds—which can get progressively challenging. So, we'd recommend you seek practice sessions with professionals, such as the 18 iOS Engineers available on Prepfully. They possess valuable insights into common mistakes to avoid and can offer guidance on improving your interview performance. Book a 1:1 session with them directly here.

Interview Questions:

• You're tasked with designing a weather app for iOS. Describe the components, data sources, and user interface elements you would include, and explain the architectural pattern (e.g., MVC, MVVM) you'd use to build it.
• How does URLSession differ from NSURLConnection in iOS? Describe the key features and advantages of URLSession, and when you would choose one over the other.
• Explain the concept of Grand Central Dispatch (GCD) and when you would use it in an iOS application.
• Given an array of integers, find the longest increasing subsequence. Explain the time and space complexity of your solution.
• Define and explain the concept of the responder chain in the context of iOS development.
• Elaborate on the differences between Grand Central Dispatch (GCD) and Operation Queues in managing concurrent tasks in iOS development.
• What are the drawbacks of using storyboards?Explain the difference between protocols and inheritance.
• Highlight the distinctions between structs and classes.
• Discuss the concept of mutating methods in both structs and classes.
• Elaborate on the differences between unowned and weak references.
• Provide an example to illustrate the concept of a retain cycle in memory management.
• Share the disadvantages of using the Singleton design pattern.
• Find the common parent of two UIViews in a view hierarchy.
• How would you design the data flow and storage mechanisms within an iOS app, considering factors like network requests, local caching, and data persistence?
• Explain your approach to designing the user interface (UI) of X iOS app. How would you ensure a seamless and user-friendly experience?
• Given two views, write an algorithm to find the closest common superview if one exists.
• How would you design a flight booking app?
• Implement a hashmap data structure.
• Design an airline booking app.
• Describe a time when you had to resolve a dispute with a teammate.
• How many ways can you implement concurrency in iOS?
• What is the difference between OperationQueue and GCD?