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Doordash iOS Engineer Interview Guide

Interview Guide Nov 07

Detailed, specific guidance on the Doordash iOS Engineer interview process - with a breakdown of different stages and interview questions asked at each stage

The role of a Doordash iOS Engineer

DoorDash is on a rapid growth mission and they're expanding their presence as a top-notch on-demand logistics engine for deliveries globally. As an iOS engineer, you'll be an integral part of this journey, contributing to the development and maintenance of their vast global infrastructure, which powers DoorDash's marketplace.

The role is product-focused, and you'll have the chance to create user-friendly and visually appealing mobile experiences. What's interesting is that you will not only be building complex apps but also have a say in important product decisions.

In terms of compensation, the average package for a DoorDash iOS Engineer is quite competitive at $280,540. This includes a base salary of $174,143, a stock grant of $105,445 per year, and a bonus of $952.

Doordash iOS Engineer Interview Guide

The DoorDash iOS Engineer interview process typically comprises the following 4 rounds:

  • Phone Screening with HR
  • Take-Home Assignment
  • Technical Phone Interview
  • Onsite
Relevant Guides

DoorDash iOS Engineer - Phone Screening with HR

Overview

The Phone Screening with HR in the Doordash iOS Engineer interview is generally a relaxed and informal conversation with the recruiter. The goal here is to understand you better. 

They may inquire about your background, past experiences, and your motivation for wanting to work at Doordash. As the conversation progresses, they might ask some basic iOS-related questions to gauge your knowledge in that domain. For instance, questions about your experience with Core Data, UIKit, or the App Store submission process could come up. Be prepared to discuss your relevant experience.

This interview round is usually not too challenging to pass. Ensure you have a concise elevator pitch, have reviewed your previous work experiences, and can provide a compelling answer for why you're interested in joining Doordash.

DoorDash iOS Engineer - Take Home Assignment

Overview

This one would require around 4-5 hours of your time and typically involves domain-specific tasks related to developing a relevant iOS application. 

For instance, a previous candidate was emailed a zip file that contained an Xcode project, a README, a JSON sample file, and a struct with a `getItemData()` function that has just three lines of code to load the JSON data from disk. The goal was to assess their coding skills and familiarity with iOS development.

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DoorDash iOS Engineer - Technical Phone Interview

Overview

The interview is conducted as a one-hour Zoom call with an iOS engineer from DoorDash. This is where you'll get the opportunity to go over the take-home project you've previously completed. The recruiter will make it clear during the initial call that this interview will largely revolve around discussing your assignment, so be sure to know it inside out.

Apart from the project discussion, be prepared for a deep dive into iOS development. The interview 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.

So, our advice is to brush up on your Swift skills, even if you're more accustomed to Objective-C.

You can also expect theoretical questions like "Frames vs Bounds?" or "What is MVVM-bindings?" If you get through this round, you'll be invited for the onsite interview.

DoorDash iOS Engineer - Onsite Round

Overview

The onsite interview is divided into four main steps, each designed to assess different aspects of your skills and experience:

  • Coding Rounds: There are two coding rounds; one involves working on the code of an existing project, and the other involves solving a domain-specific problem related to iOS development. Both of the coding rounds will happen on the laptop. Consider it an opportunity to demonstrate your problem-solving skills, understanding of iOS concepts, and your coding abilities under time constraints. It's also important to focus on code quality, maintainability, and scalability. Plus, make sure to communicate your thought process clearly to the interviewers.
  • System Design: The final architecture interview is about assessing your ability to design complex software systems. You may be given a scenario or problem to solve that requires you to think about the big picture, including scalability, performance, and maintainability. You will also be expected to demonstrate your understanding of system design principles, scalability, and architecture best practices.
  • Behavioural Round: This is where they get to know you better as a candidate. You can expect questions about your background, experience, and how you've handled various design challenges in the past. It's important to highlight your communication skills and teamwork abilities during this phase.

Some of these interviews can be quite lengthy, often lasting over an hour. The interviewers are looking for candidates who not only write code but can also design it properly, debug effectively, and have a good understanding of networking concepts.

Interview Questions

Interview Questions:

  • 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.
  • Explain the key differences between the Model-View-Controller (MVC) and Model-View-ViewModel (MVVM) architectural patterns.
  • Clarify the distinctions between escaping and non-escaping closures in Swift.
  • Define and explain the concept of the responder chain in the context of iOS development.

Doordash iOS Engineer Roles and Responsibilities

Following are the roles and responsibilities of a Doordash iOS Engineer:

  • You will collaborate with product teams to build and enhance features for DoorDash's mobile app. This involves not only coding but also effective communication and teamwork
  • Improving the codebase is a crucial aspect of this role. You'll be expected to contribute to code quality by continuous refactoring, making the code more maintainable and efficient.
  • Doordash deals with real-time data transfer and challenges. Expect to work on solutions that ensure smooth and seamless data exchange, especially in a real-time context.
  • You'll extend and implement APIs, which are essential for the app's functionality. This includes integrating with backend systems and ensuring data flows securely and efficiently.
  • You'll be responsible for implementing unit tests to ensure that your code is reliable and functions as expected.
  • You need to stay up-to-date with industry standards, best practices, and the latest tools and technologies in iOS development.

Doordash iOS Engineer Skills and Qualifications

Here are the skills and qualifications that a Doordash iOS Engineer must have:

  • A MInimum of a Bachelor's (B.S.), Master's (M.S.), or Doctorate (Ph.D.) degree in Computer Science or an equivalent field.
  • A track record of at least 5 years in the software development industry, demonstrating your expertise and commitment.
  • Mastery of the Swift programming language and in-depth familiarity with the iOS Software Development Kit (SDK
  • Sound knowledge of systems architecture and object-oriented programming concepts. 
  • Proven experience in the complete app development lifecycle, including building, launching, and iterative improvements on mobile apps.

Frequently Asked Questions