The good:
(and it is VERY positive part) I really loved to talk to the real engineering. Seems really bright guys, relaxed in talking and very open personalities. I truly wish I could work with them on some projects in a future.
The bad:
Overall was entirely chaotic and random. My application got lost few times in their system, multiple "pings" was simply ignored. But nevertheless seems later they finally "woke up" and wrote me few auto-generated messages to setup a first meetings.
The hiring personnel feels pretty clueless from what they want from you, so they are trying to redirect to others, who are less clueless than them. The company feels fundamentally broken at management, because even software managers seems helping their HR to do their hiring process and finding your application. The overall feeling is that you're dealing with a pretty low-grade amateurs that got lost and has no clue what to do with you.
The ugly:
After number of few very positive talks with the tech people and scheduling on-site final interview, they suddenly answered me with an automated junk mail "we are fast growing company, we are very cool, we have overwhelming applicants, you are loser, try something else" (all that typical Greenhouse auto-generated templates thing) and went ghosts. Not even a personal written "sorry, yeah, but....". It felt totally disgusting and cheap.
Recommendation to applicants:
Listen carefully to Cloudflare themselves. As they say in their own autogenerated no-reply junkmail, they are "very busy and fast growing up company", and as they say "a lot of companies hiring out there", just do a favour to yourself: stick to their advise. Let them grow up on their own and go apply somewhere else instead. :-)
The interview question:
Was very easy for me, since all what they do is what I do all day long anyway. Nothing new and special, something I knew much better than their engineers. But something might be hard for you, though, I don't know...