Tinder iOS Engineer Interview Guide

This is typically a super casual conversation with the recruiter whose aim is to get to know you better. He/she might inquire about your background, experiences, why you are interested in working at Tinder—and then move to asking some basic iOS-related questions to assess your knowledge in that area. For example, they might ask about your experience with Core Data, UIKit, or App Store submission process.

This round is mostly easy to get through; make sure you are prepared with a crisp elevator pitch, have reviewed your past experiences, and have a compelling answer for why you want to join Tinder  

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. 

Make sure you review fundamental iOS development principles, iOS-specific concepts and best practices before this round. Communicate effectively with your interviewer and prepare examples of your prior experiences beforehand to drive the interview in a favorable direction. 

• How would you implement network communication in an iOS app using URLSession?
• Write code to parse JSON data in an iOS app. Consider error handling and extracting specific data fields from the JSON structure.
• Explain the concept of asynchronous programming in iOS development. 
• Provide an example of when and how you would use Grand Central Dispatch (GCD) or Operation Queues to handle background tasks.
• Describe the process of handling user input validation in a form or input field within an iOS app. 
• What are the steps involved in integrating a third-party library or SDK into an iOS project? What factors would you consider when choosing between using CocoaPods, Carthage, or manually integrating the library?

The on-site interview is a comprehensive round that typically lasts around 4 hours. You can expect a technical round (data structures and algorithms), a system design round, and a behavioral round. In addition to this, there is a case study round which we will discuss ahead. 

Data Structure/Algorithms Round

The data structure/algorithms round typically focuses on evaluating your problem-solving skills and understanding of fundamental concepts in context to iOS app development. You may be thrown multiple technical questions which revolve around analyzing algorithmic complexity and applying data structures effectively. Candidates are typically asked to write code on a whiteboard, share their thought process, and explain their solution.

You can also expect questions related to iOS development principles, memory management, and Swift. Further, they may ask about your past projects or experiences with building user-facing features, working with autolayout, utilizing architecture patterns like MVVM/Clean, and so on.

Here's are examples of questions asked during this round:

• Implement a function in Swift to reverse a linked list. Describe the time and space complexity of your solution.
• Explain the concept of a hash table and its advantages in iOS app development. Provide an example scenario where a hash table can be useful.
• Design a data structure to efficiently store a collection of user profiles in memory. Discuss the trade-offs of different data structures and justify your choice.
• Given a binary tree, write a function in Swift to determine if it is height-balanced. Describe the algorithmic complexity of your solution and explain how you would test it.
• Implement a depth-first search (DFS) algorithm for traversing a graph.
• How would you optimize the memory usage of an iOS app to prevent excessive memory consumption and potential crashes?

Here's 3 tips to prepare for this round:

1. 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.
2. Engage in coding practice to sharpen your problem-solving skills. Solve coding challenges from platforms like LeetCode or HackerRank. Focus on algorithms and data structures commonly used in iOS development. Be prepared to explain and discuss your solutions.
3. Study iOS development principles, memory management, and Swift language features. Review topics like autolayout, UIKit, memory optimization techniques, and design patterns like MVVM/Clean architecture. Be ready to discuss your experience with building user-facing features, working with frameworks, and handling app performance.

Tinder iOS System Design/Case Study Round

Now, this round follows an interesting format and involves a hands-on coding task. You are given a prompt for an app to develop within a couple of hours—which is essentially a test of your coding skills, app development capabilities, and problem-solving skills. Your interviewer(s) wants to assess your ability to solve complex iOS engineering design problems and architect high-level solutions

For instance, you might be given a prompt to develop a feature that enhances the matching algorithm in the Tinder app. This feature could involve implementing a recommendation system that suggests potential matches based on user preferences, interests, and previous interactions.

Around halfway through the on-site interview, there will be a lunch break or check-in—following which you will participate in a group interview with four engineers. 

This is when your coding task will be reviewed; they'll assess your technical decision-making, design choices, and the quality of your code. They might ask you a bunch of questions such as how you handled potential edge cases in the app, the trade-offs you considered, the scalability of your solution, and so on.

They are looking for three key things:

1. Technical skills: Demonstrate your knowledge of various technologies, understanding of tradeoffs and system interactions, and the ability to build flexible and scalable solutions.
2. Structure and approach: Show how you scope the problem, clarify requirements and constraints, apply principles like MVVM and MVC, and understand the business problem and its impact on use cases. Take an active role in driving the discussion and avoid making assumptions without discussing them.
3. Communication and collaboration: Interact effectively with your interviewer, explain your thinking in the right level of detail, and approach problem-solving as a partnership. 

Here are 5 tips to excel in these types of interviews:

• Scope and clarify: Narrow down the broad question into manageable parts that you can address within the given time frame.
• Employ a structured and methodical approach: Divide your solution into distinct layers such as View, Controller, Network, Storage, and Cache, mirroring real-life system design.
• Watch out for cues: Look for hints from the interviewer that may indicate potential complexities or alternative considerations in your design. For instance, if you're discussing the implementation of a messaging feature and the interviewer asks, "How would you handle message attachments?", it's a cue that there might be additional requirements or technical challenges related to file handling, data storage, or network communication. Take this opportunity to explore those aspects or seek clarification, showcasing your ability to think beyond the initial problem statement.
• Think out loud: Vocalize your approach and reasoning as you tackle the problem. This helps the interviewer understand your thinking process and provides them with an opportunity to guide you if you stray off track or pursue a line of thinking they are not interested in.
• Practice: 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.

Behavioral Interview

The behavioral portion of the interview is designed to evaluate your collaborative skills and assess how well you align with Tinder's core values. During this phase, the interviewers may inquire about your previous experiences, your problem-solving approach within the realm of iOS development, and evaluate your communication abilities.

If you go through Tinder's company page, you’ll learn that Tinder's mission is to "keep the magic of human connection alive." They strive to help people make meaningful connections with others. Therefore, it's a good idea to highlight the importance of a user-centric mindset in development to facilitate this. For instance, you can talk about how you believe in incorporating user feedback into your decision-making process to deliver personalized and inclusive app experience. Or that prioritizing features that facilitate meaningful interactions between users is paramount.

Make use of questions in connection to your past experiences to demonstrate how you've emphasized on the above mindset and values. Also, think ahead and provide specific, concrete examples of times you've displayed excellent team management, conflict resolution, and communication skills.