I applied online. The process took 2 months. I interviewed at Wolt (Berlin)
Interview
The process consists of 4-5 rounds: -HR round just to explain briefly your interests in the position and your experience. -Interview with the Director of Data Science. It's just more behavioural and talking about previous experiences but more detailed than the previous one. Don't need to prepare anything, just try to be kind. -Home Task Assignment. This depends on the type of role, in my case was Personalisation and Search. They provided a dataset with 4k user sessions data alongside a venue dataset with some info about the restaurants(rating, conversion rate, impressions...). The challenge was divided into 4 main tasks and it is the typical DS assignment: EDA, Modelling part (in this case you needed to create learning to rank model: first a baseline like a ranking sorted by popularity and then a ML-based model) and conclusions focused overall in detecting bias such position or popularity ones. I couldn't finish the task at time because I had some doubt about the way the data was given and how it could be used and they were flexible and gave me one more week(even this was estimate for a one week deadline). Also you need to prepare a complementary presentation. - Technical Interview: If you have passed the case study, then you are moved to the technical interview. Theoretically you should present the case but that was not my situation. On the other hand, the asked some foundational questions about ML basics like data leakage, confusion matrix and get the probability from a classifier problem (Bayesian rule) and other simple questions about recommendation and ranking. Please, prepare this part because they don't warn you about this and you can think is about the case presentation and is not the case. -5th round: I don't know exactly how this is because I didn't reach this stage. But I think is something with a higher level manager or meet the team round to have some match with you. In general the people is great and the process is somehow smooth but it take long time and specially the tech interview could be disappointed. You can feel that if you take more time answering something or give you some hints this could be the ultimate factor to withdraw your application although your case study was satisfactory. In my opinion, when there are multiple candidates in this last stage, this small details marks the difference, making all your previous work worthless. I think it should be more balance towards the case study because it is closer to what you might expect in the potential role rather than questions that could be checked and studied with resources. This is my complaint about the hiring process. Finally, I received some kind of soft rejection saying that I could be a good fit and this doesn't mean the end of our relationship but after confirming that I would be interested in continuing being in touch, I didn't receive any answer. Quite hypocritic from their side. Make a good case study to raise the bar and prepare some foundational concepts about DS and specially some basic for your specialty.
Interview questions [5]
Question 1
1: How would you add additional user/item features in a factorization matrix for recommenders?
3: You have website/place that gets 10% of conversion. Given a classifier model that predicts if an user will convert or not, with a true positive rate of 1 and true negative of 0.5. Say which is the probability of getting true positive values.
I applied through a recruiter. The process took 2 weeks. I interviewed at Wolt in Aug 2025
Interview
It's roughly a 4-part process.
There's an interview with the recruiter followed by an interview with the line manager/hiring manager. Then there's a take-home case-study/assignment followed by a wider discussion around that to assess technical competency.
I was cut after the interview with the hiring manager and the reason given was that there were more competitive candidates available.
I personally felt that the hiring manager had already made up their mind before the interview and that there was ethnic discrimination against me in the hiring process. For confidentiality i will refrain from discussing my and the interviewer's ethnicity.
Overall the process felt like an interrogation rather than an interview.
For stages process: HR screening, hiring manager, product manager, data science team. All the interviews (except HR) are built around experimentation. The last stages consist of case studies, with no technical or whiteboard questions.
Everybody is nice and collaborative, although the whole process took a month.
Interview questions [1]
Question 1
A/B tests, and their alternatives (causal inference, etc.): what experience do you have working with them, how do you implement them, and what are the limitations
I applied online. I interviewed at Wolt in May 2024
Interview
The interview steps were clearly laid out from the beginning, which helped me prepare effectively.
What stood out the most was the promptness and efficiency of the entire process. The Talent Acquisition (TA) team maintained thorough coordination, ensuring that everything went smoothly and on schedule.
The technical round was somewhat confusing because the focus was minimal on the take-home assignment, with the discussion largely dominated by product-related questions. This shift in focus led to misunderstandings regarding expectations and answers. It also undermined the purpose and time invested in the take-home assignment.
Interview questions [1]
Question 1
The interview included several questions, among which were the following:
1) Hiring Manager Round:
- Describe a time you resolved a conflict.
- Provide a couple of business guesstimates.
2) Technical Interview:
- Devise marketing strategies to promote the app in a specific area.
- Mention the KPIs you would track.
