Interview Guide for BackEnd Engineering

General Info

We will ask you to complete 3 problems within 90 min timeline. You will have 20 minutes to complete section 1, and then 70 minutes to complete both sections 2 and 3.

• General knowledge questions [15 multiple-choice questions]:

  1. Testing Techniques

  2. System Design

  3. Microservices

  4. REST API

  5. Problem-Solving

• Coding problems related to:

  1. Algorithms & Data structures

  2. REST APIs

• Make sure you finalize your work before moving to another problem.

• Once you complete a section you won’t be able to go back.

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

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 both 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 language agnostic so make sure you use your strongest coding language.

• 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 will 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 coding interview is based on the home task sent to you by your recruiter. You are asked to send your solution back to us (your recruiter or coordinator).

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 submitted before the interview. Using your strongest programming language, we will ask you to complete a couple of tasks (extensions) related to the original problem and explain your thought process.

Worth remembering

• Address all requirements in the task;

• Cover test coverage for happy and sad paths; 

• Be ready to share your screen during the interview;

• Send your solution back to us at least 48 hours before the interview.

Interview Structure

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 part | 25 – 30 min | 2-3 tasks 

Come with your solution set up in your preferred development environment, ready to work on extending it. We will ask you to complete a couple of tasks that build upon the code you submitted so you can show your coding skills, specifically back- end 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.

Assessment rubrics | What interviewers look at: 

Coding – try to complete the tasks by using the framework of your choice to its full potential.

Problem-Solving – as there is a time limit associated with this interview, try to get the main task accomplished even if it means you’re 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.

Testing – testing code is important and something we do at Deliveroo. Show us how you do testing or talk through it if there isn’t 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

Please note that for Staff Engineering roles we are currently trialing a new live coding interview for which you won’t have to complete a test assignment. If you applied for a Staff role your recruiter will be reaching out to you directly with further details.

There are hundreds of services worked on by dozens of engineering teams and they all need to work seamlessly together to get that burger to you at 7pm on a Friday. This means it’s really important that our engineers can reason about and design complicated interacting systems that can handle the scale Deliveroo operates at.

Response framework:

• Clarify the problem. 

• Break down a complex element into parts.
  Identify components.

• Discuss and iterate on your solution with your interviewer. Identify and analyse design trade-offs.

Your interviewer will ask questions to dive deeper into some parts of your design.

How to prepare?

• Read up about web platforms that operate at a large scale; how do they manage many requests? How do they cope with things that go wrong? Check out our post!

• Try out system design problems on the web!

• Feel free to use any stack you’re familiar with, we’re interested in why you make the choices, not what choices you make.
  Be ready to discuss how your decisions affect the user of the platform you’re designing and any trade-offs you’re making.

• Get familiar with a whiteboarding tool (we recommend Draw.io!) Prep your device so you are ready to share your screen.

   

Additional Tips

Communicate, ask questions, discuss your thoughts, and speak about any problems you’re having. Engineering is collaborative – so is the interview. We’re interested in how you approach problem-solving. Think out loud. Ask questions and state your assumptions.

Start at the high level and work down to the detail. Architectures take much longer than an hour to build “in real life”, your interviewer will steer you to different areas of your design to get a better understanding of your strengths.

Use what you know. You might have worked on a similar system in the past, or you might not, either way, don’t feel like you should use a particular type of architecture.

This interview looks at how you handled specific challenges in the past to assess if you will 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)

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

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

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

• Main obstacles that 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)

• Specify the situation, differences of opinions and other important context. 

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

• How this discussion ended and impacted your future cooperation?