Went through a fairly standard interview process, phone call, then a take home test followed by a face to face with senior developers and founders. All went well and received an offer in writing, I didn't attempt a salary negotiation I (somewhat amateurly) asked if the offer was open to negotiation, they then told me they would get back to me. A few days later they responded by saying the offer was firm but that they were sorry it wasn't going to work, the wording of the email implied the offer was off the table and that the process was over ("All the best with your search, stay in touch" etc) . I was shocked that they would pull the offer at the mere sign of a salary negotiation, so I probed further as at that point I was still interested. Managed to get a face to face with the CTO, after talking for some time he finally admitted in the time it had taken to feedback about the negotiation they had finalised lower offers to some other engineers, so of course they were looking for a way out of my offer. I left the meeting confused about where I stood and still to this day don't know what they wanted from me. Ultimately I figured they cared more about saving a few pounds than honouring their written word or having a positive candidate experience. Not a company worth trying to "defuzz" the situation with.

There is something going on here, I have similar views as the two other candidate here. They give you a take home with some performance related work and never bother to come back to you. They have monolith system and i have worked in massive microservice based distributed systems and especially the performance area. I was atleast expecting a review of what i have sent. But this never happened they didnt even bothered to respond back. This definitely says that they are just collecting information and have no interest in hiring. Make sure you understand this point before going through this exercise. As you are most likely going to waste all your time.