I applied online. The process took 2 weeks. I interviewed at Lightspeed (Montreal, QC) in June 2021
Interview
The process is composed by :
HR interview
Technical interviews
Team leaders interviews
The HR was available all along the process answering questions and providing feedback and different information
The technical interviews are about knowledge data architectures, databases, data on cloud ... and live coding. The goal of these interview was to know the person, how she thinks , reacts facing some difficulties and responds too feedback on her code or answers not just if the answer is correct or no
the interviews with team leaders were about company vision, technical challenges, culture and values.
All the process were done with kindness and honesty
It was an excellent experience
Interview questions [1]
Question 1
number of children of a node in a B tree
indexing on parquet file
I experienced the interview process as very disrespectful. Only during the feedback conversation after my rejection did I learn that the position had effectively shifted toward a mid‑level role, something that had not been communicated to me beforehand. I was told that this feedback that I am, somehow, actually a mid level developer (despite covering the job of a senior) was told to me “for the sake of my future.” In my view, questioning a candidate’s seniority, especially when they have already held comparable roles for years, is inappropriate. I ultimately accepted a senior position elsewhere with higher compensation and full remote, without mandatory “pillar days” of attendance or whatever you called it. For me personally, remaining unemployed would have been preferable to working here.
Interview questions [1]
Question 1
Mostly technical coding questions that in my opinion really relied on mnemonic knowledge and became obsolete after LLMs
I applied online. I interviewed at Lightspeed (Berlin) in Feb 2026
Interview
The process started with an initial screening round, followed by a technical interview with system design and then a round with deeper technical discussion with code review. The team was professional and direct throughout the process. Communication from HR was clear and timely.
The interviews were heavily focused on core Python fundamentals, concurrency concepts, messaging systems (queues, Kafka/RabbitMQ), transactions, and system design. The technical depth expected was quite high, especially around language-level concepts such as context managers, decorators, and concurrency primitives.
In the later round, the discussion became very detailed around Python internals and low-level constructs. When I wasn’t able to confidently explain a specific core concept (context managers), the interview was concluded early with the feedback that for a Senior role, strong fluency in core Python fundamentals is expected.
What I liked:
Interviewers were technically strong and clearly knowledgeable.
Questions were practical and relevant to backend engineering.
Clear feedback was given directly.
What could be improved:
The process felt somewhat unforgiving; the interview was ended early based on one foundational gap rather than evaluating overall system design and backend experience.
A slightly more holistic evaluation of seniority (architecture, real-world impact, problem-solving) alongside language fundamentals would make the process more balanced.
Interview questions [1]
Question 1
Decorators
Concurrency (GIL, threading vs multiprocessing)
Transactions and atomic operations
Messaging systems and delivery guarantees
I applied through an employee referral. I interviewed at Lightspeed (Amsterdam) in Jan 2026
Interview
The interview process consisted of a recruiter prescreening call, followed by an interview with the engineering manager, and finally an in-depth technical interview focused on problem solving, system design, and practical engineering skills.