What’s the feature building interview?

It’s a 1-hour online pair programming session. You will meet 2 engineers at Doctolib and be asked to solve a coding problem using an online IDE (Coderpad), where you can choose from JavaScript, Ruby, TypeScript, Python, C#, Rust, or Java.

How does it work?

The feature building is an iterative exercise. You will be asked to follow a TDD (Test Driven Development) approach during the interview.

At the beginning, we will provide you with a test case: your goal is to write (from scratch) an algorithm that passes the test. Then, if you solve the first test case, we will provide you with a second test case, which will require you to go back to your code and make changes to pass the new test. Again, if you pass the second test, we will provide you with a third one, and you will follow the same process, iteration after iteration. After each test case is solved, we will also give you time to refactor your code.

In total, there will be 6 iterations, and as you move forward, complexity will gradually increase. We will spend the first 45 minutes getting started and solving the test cases, and the last 15 minutes discussing your final solution and leaving space for your questions.

During the last 15 minutes, while reviewing your code, we won’t ask you to change anything or refactor it—we just want to have a conversation about your solution. We will be curious to know what you would do if you had more time to work on it, for instance, or if there’s anything you would like to change to make it production-ready, or if you see any edge cases you would like to add. We will take your final suggestions into account in our assessment too!

How can I be successful?

As mentioned, there will be 6 iterations (i.e., 6 test cases) you will be asked to solve during the interview. Try to do your best and solve as many cases as you can, but please keep in mind that there is no specific number of iterations we expect you to solve to be successful, as we assess not just the number of passed cases but also many other qualities we look for in software engineers.

In particular, we look forward to seeing strong communication and pragmatism during our time together, and we strongly advise you to focus on those two areas to have a great interview.

Regarding communication, it’s important to not just solve the problem, but also explain what you are trying to do and achieve with your code. Focus on reasoning out loud: explain your thought process and make sure the interviewers understand what you are trying to do at each step. Be vocal during the exercise and proactive if you have questions, doubts, or encounter any blockers. Sometimes, interviewers will try to offer guidance and help as well, and being open to feedback is also a quality we appreciate. Clear and effective communication will be key to working in every engineering team at Doctolib.

Regarding pragmatism, go for simple solutions first and only add complexity when needed. As mentioned, this is an iterative exercise. There is no need for you to solve the whole problem in advance or to care about issues we didn’t ask you to solve. At the beginning, there will be just one test case in front of you, and we want you to make it pass as quickly as you can. Keep your code simple and try to not over-engineer your solution – your code doesn’t have to be perfect! Just focus on the test case you are currently asked to solve: this way you will be able to move forward quickly. Iteration after iteration, the exercise will gradually become more complex, and you will have the chance to work on your code and improve your solution.

In the end, we will assess you not just on the what (how many test cases you have solved), but also on the how (your communication, pragmatism, problem-solving skills, code quality, and suggested improvements). Both dimensions will be key for you to pass your feature building interview!

Frequently Asked Questions

1.What tools will you use during the interview?

We will use Coderpad, an online IDE. At the beginning of the interview, we will ask you what coding language you want to use, then send you an invitation link to join the platform. No need to install anything.

2. Which coding languages can I use? Can I select any libraries or frameworks?

You can use one language from the following list: JavaScript, Ruby, TypeScript, Python, C#, Rust, or Java. You don’t need to use any framework or external library. As the coding exercise is simple, you will just need the “vanilla” language.

3. What if I’m rusty on the language I have chosen?

Don’t worry about it. We’re not assessing your knowledge of a specific language (JavaScript, Ruby, etc.) or library, we’re just assessing your coding skills. Interviewers will help you with the right syntax whenever you get stuck.

4. Can I use external resources for help?

Sometimes, your interviewers might not be able to help with syntax, but don’t worry at all. You can use external resources such as Google, StackOverflow, etc. to get the right answer. When you do this, just make sure to tell the interviewers.

5. Can I use AI tools for help?

For the moment, no. We believe in the great value of these tools, but we are still assessing how we can integrate the usage of AI in our interviews, as we are working to become an AI-driven healthcare tech company.

6. Do I need to prepare my solution in advance for this interview?

No, you don’t need any preparation. As mentioned, the interview will be an iterative and test-driven exercise. We want you to solve the problem step by step during the interview. Preparing a solution before the interview might just lead you to over-engineer and solve unnecessary problems, while reducing your problem-solving flexibility during our time together.

7. Then, why do you share the exercise in advance?

We value being transparent and want to give you an idea of what the topic of the problem will be. We want candidates to feel comfortable while reducing uncertainty, but we do not want you to solve the problem before the interview.

8. Who will be my interviewers?

You will meet two software engineers in our organization. It can be anyone from the Doctolib engineering teams. All feature building interviewers are trained to run this interview, and their seniority will reflect the seniority of the role. Many times, interviewers can be from different countries too (France, Germany, Italy, The Netherlands…).

9. Is the interview run in the English language?

Yes. We are an international company and we expect everyone to speak English.