Interview Guide for Mobile Engineering

Your recruiter will share a link to our Hackerrank task where you will be able to do all of your work.

General Info

• We will ask you to complete 3 sections within a 60 to 90 min timeline depending on the question set. The sections are:

  1. Android-focused multiple choice questions section (5 questions)

  2. API Knowledge multiple choice questions (2 questions)

  3. REST API Coding task

❕Pro tip! In the coding test, modern Android development libraries (Retrofit, Ktor, etc) for network operations are not available. If you need to perform a network request, the simplest way is to use the java.net.URL class.

• You will be able to jump back and forth between problems, so don’t panic if an improvement comes to mind unexpectedly.

• Don’t forget to submit your solution before the time expires.

• We do care for quality, keep that in mind. This is not one of those assessments where you have to do a lot to complete it quickly.

• There is no need to write tests, HackerRank will run tests and checks to see how many of them your solution passed.

• Heads up: There is no debugger on this platform. You may have to find another way to see what your code is doing.

A few things to cover before you start

• Familiarise yourself with the Hackerrank environment first so you can do your best on the day. Make sure you check all sections, before and during the interview. The goal is to eliminate any unnecessary surprises. We want you to focus only on the task at hand.

• Our interview problems are not language-agnostic. You will have to use Kotlin in the assessment.

• The tasks are timed so make sure you set your working environment accordingly and you won’t be disturbed.

• A significant percentage of your success will rely on system familiarity. It may be a good idea to do a warm-up task beforehand so you are in the right frame of mind and have a good understanding of how everything works.

This is no secret but the interviewing environment is slightly different from your day-to-day work. With this in mind, make sure you spend some time on preparation. Those who practice, perform better.

Take a look at the Interview Preparation Kit and warm up a little before your big day.

The task will be fully iOS focused. Your recruiter will ask for your Github username to be able to send you the test assignment.

Completing this exercise will help us understand your iOS skills before the interview. It’s designed to replicate everyday work, but within an example movie app. You’ll complete 2 tasks:

• Code review an existing change
• Add a small feature to the app

The coding interview is based on the home task sent to you on Github. 

During the interview, the conversation will start with a short introduction. After that, we will move to the technical part of the interview where we will be reviewing a coding solution you have submitted before the interview. Using either Kotlin or Swift (depending on your domain), we will ask you to complete a couple of tasks (extensions) related to the original problem and to explain your thought process. Before the interview, please make sure you are able to share your screen, specifically in Google Meets. Also, for the coding interview please have the iOS/Android-code-test repository open and the feature/search branch checked out.

Interview structure

• Short intro (5-10 min)

• Pair programming session (45 mins)

• Short Outro and Questions (10 mins)

Solution walkthrough | 10 – 15 min

This part focuses on your introduction to the submitted solution. We would like you to explain your thought process during our interview, and any considerations or alternative options you had in mind when working on it.

Extension work | Live coding | 35- 45 min | 2-3 tasks

The task which you will focus on is a relatively short exercise where you will have to show your coding skills, specifically iOS/Android coding skills. We suggest you brush up on those to make your skills shine during the interview. We don’t expect you to complete the entire task, but keep the time in mind. More practice equals less stress.

Assessment rubrics | What interviewers look at

Coding – try to complete it using either Swift or Kotlin depending on your domain.

Problem-Solving – as there is a time limit associated with this interview, try to get the main task accomplished even if it means you are not producing the best code. Be sure to communicate this.

Communication – ask questions, and discuss your thoughts or any problems you’re having. Engineering is collaborative – so is the interview. If there is not enough time to code it out, at least go through it verbally.

Testing – testing code is important and something we do at Deliveroo. Show us how you do testing or talk through it if there is not enough time.

We are interested in learning how you work and solve problems therefore we expect this submission to be fully done by yourself. In this instance we say no to AI – all AI-generated submissions will be rejected.

The following are not allowed during a live coding interview:

• Ask ChatGPT or similar to explain compiler or runtime errors or write code.

• Use Copilot or similar to explain or generate code

The interviewers will be there to describe the problem, give clarifications and ask broad, guiding questions. Treat them as a fellow engineer and Product Manager combined and do feel free to clarify any requirements that may help you decide between different designs.

The main purpose of this interview is to assess your architecture design capabilities but that includes several other aspects too, like:

• problem-solving

• communication

• platform-specific considerations

• product decisions

• post-release considerations

Additional Tips

Communicate – Ask questions, discuss your thoughts, and speak about any problems you’re having. Engineering is collaborative – so is the interview.

Drawing diagrams might be helpful but isn’t required – Your thought process is more important. Start at the high level and work down to the detail. Try to cover the subject in detail where possible.

We use Excalidraw as a whiteboarding tool for you to draw diagrams or make notes. Please take a few minutes to familiarise yourself with it before the interview.

This interview looks at how you handled specific challenges in the past to assess if you would be a good match for the role. Some of the areas we address are:

• Communication 

• Team management 

• Leadership 

• Problem-solving

• Flexibility and can-do attitude Initiatives and growth mindset

• Organisation and self-development 

• Decision making
  

We care about our culture as much as we care about our products! Have a look at our Deliveroo Values:

Live and breathe our marketplace 

Being deeply immersed in all sides of our marketplace, and each and every neighbourhood we serve.

Play to win

Setting bold targets and seeing them through with tenacity, creativity and grit.

Celebrate difference

Advocating for respect and fairness for everybody, understanding we are all individuals on a unique journey.

Champion big and small innovations 

Innovating no matter what our role is, and celebrating achievements no matter the size.

Obsess about operational excellence

Leaving things better than we found them, investing both our time and money in the things customers care about.

Be curious and intellectually honest

Thinking deeply and debating each other with respect while keeping our biases in check. 

Take a look at our few examples

Tell us about a time when you failed to meet a deadline. What did you fail to do? What did you learn? 

Before answering have a think about:

• The root cause.

• Why did it seem like a good idea at the time? 

• How did you apply what you learned afterwards?

Describe to us a specific task or a challenge that you were facing and how you made sure in successfully completing it. What were the key factors of this success? 

Before answering have a think about:

• Being clear up front about your objectives and wider context.

• Reasons why you chose those particular strategies and tools to complete it.

• Any measures you had in place to monitor your progression.

• Main obstacles you had to address and things learned along the way.

   

Provide an example of the time when you had a difference of opinions with one of your colleagues regarding a project you both worked on and how did you arrive at the conclusion. 

Before answering have a think about:

• Specifying the situation, differences of opinions and other important contexts. 

• What data, tools or information did you use to support your idea?

• How did this discussion end and impact your future cooperation?