This may be a very easy interview if you have the specific experience tested. HubSpot only appear to ask canditates 2 main questions of the same 3-4 questions repeated in other comments. The questions test your experience in basic application design, some experience with REST, RDBMS, and optimisation. For the optimisation, the questions require high-level answers like propsing implementing a cache, as opposed to time/space complexitiy questions. Giving the appropiate answer on both these main questions quickly seems to be by far the most important aspect of the interview. I had not prepared well for other questions on my job experience, but the feedback I received focused only on the 2 whiteboard questions. As I said the other questions don't seem to be very important, but I'd recommend preparing some likely answers using the STAR technique. I did this after my interview and was able to come up which much better answers to the ones I gave at the time. I was hinted at by the recuiter to research the answers to the questions they ask. In hindsight I wish I had done this better, as the questions are relatively simple, but you are given little time or scope to improvise during the interview. There is also a pre-interview test, I won't write much about here, the details are covered in several of the other comments. That test appears to be mainly about how fast you can finish. The code I ended up submitting for this was nothing to be proud of, but was submitted fast enough to get me to the next phase.