I don't usually leave reviews, but I felt this was worth sharing in the hope it helps future candidates and gives the company useful feedback. This is about the process and my experience, not the outcome.
The process has multiple stages. The first stage is a call with the recruiter, covering a lot of standard screening questions, which was fine and as expected. Went well.
The second stage was a 45 minute conversation with a senior member of the team. For a process with multiple stages, 45 minutes is not enough time to properly evaluate a candidate or to give them a fair chance to answer in depth. Every second stage interview I've had with other companies has been at least an hour. A large portion of the start here was also taken up by an introduction to the interviewer and the company. While useful, it ran long enough that the rest of the interview felt rushed, and I was left with around three minutes to ask my own questions, which doesn't give a candidate a fair opportunity to assess fit in both directions.
The feedback I received was that I lacked sufficient A/B testing and experimentation experience. Based on my notes from the interview, A/B testing was not actually covered well. A/B testing spans areas like experiment design, hypothesis setting, sample size and significance, and reading test results. None of these were explored. The technical questions focused more on data querying, which is a separate skill set. Being rejected on a basis that wasn't directly assessed felt unfair, and a clearer or more accurate reason would have been more constructive.
I'd also note the communication. It took almost two weeks and multiple follow ups from me to receive a response after the interview. Companies rightly expect candidates to be respectful of their time and to communicate well, and candidates deserve the same in return. A simple note confirming the decision or timeline would have made a real difference and would have been more respectful of my time and effort that went into the preparation.
None of this is about not getting the role. It's feedback on interview experience and lack of communication, in the hope the process improves for others.