Pre-face: Job opening was "Software Engineer"; found out during the on-site that most interviewers (including the CTO I originally spoke to) were specifically looking to hire a devops engineer, not software engineer.
First interview was over the phone with the CTO; I honestly thought at the time he did a decent job selling me on the company, interesting challenges they'd be facing in order to further scale out their product, etc. He explained that their goal for new work was to ensure there would be scalable build processes along with a solid infrastructure to back them up. I had asked for clarification, since it seemed at the time like he was speaking more toward a devops role, if the role I had applied for would be software/backend focused, because I want to focus less on devops, he assured me it was.
Next he set up an on-site interview: approx. 5 hours with up to 7 people, incl. him. I asked over email for a broad overview of the kind of concepts to expect questions about (obviously I wouldn't get specific concepts, but an idea of how to prepare). The response I received contained: "Our interview is a mix of pair programming, algorithm, and software design problems with 5 members of the engineering team."
I thought OK, that's fairly standard for a software engineering role, I'll just do my regular prep.
Interview day arrived, I came in a bit early for my appointment. Right off the bat in the first block with the first interviewer, the questions seemed to lean more towards networking, which I thought made some sense, because as a software engineer you should have some high-level understanding of it. Soon I was told "oh we're hiring specifically for a devops engineer."
I thought "uh.. hm.. that's strange, I thought I applied for the regular Software Engineer opening, but I guess I'll go along with it for now."
As the interviews went on, multiple of the engineers and managers I spoke with implied or actually said they were looking for a DevOps engineer who could help with future goals. I was mostly asked questions on Networking (in questions section).
It got to the point where I knew for sure they had brought me in under false pretenses, giving me the impression they had software engineer positions to fill, but instead purposely prepped specifically for a devops candidate.
Finally, in the 6th hour of my on-site, I got the chance to speak with the CTO, again, and off the bat he started me with a major technical question on something not listed on my resume, whatsoever. He began to drill into it and started to hand off the whiteboard pen, yet I had to say I don't have understanding of said topic (typically what you have on your resume is what you feel comfortable answering..). I mentioned my thoughts from earlier in the day, that there may have been some miscommunication regarding roles, etc. He responded how they want to grow their operations team. The previous interviewer also clearly didn't enjoy knowing I wasn't an expert in ops-specific knowledge.
I will admit while interviewing a candidate it can be useful to ask probing questions on unfamiliar subjects that they may not be an expert in in order to gauge reaction and how they respond. Personally this entire interview on-site went beyond that, as questions about similar concepts were repeatedly asked in varying levels of depth.
The CTO proceeded to finally ask an algorithms question dealing with recursion. The problem is, after 5 hours of interviewing, especially on topics I'm not familiar with I wasn't able to produce any type of answer. This was after 5PM, I hadn't eaten lunch (just a late 10PM breakfast, maybe my fault).
Later when I asked why I was having network questions directed at me, the CTO hinted/implied it had to do with where I work (won't say here, sorry). But I found that question to be quite ridiculous. I work at a company with over 70k employees. Just because the main product there has historically been network/network hardware-specific doesn't mean my org for my current role, or my current role itself, deals with said networking hardware. None of that was true, my work and focus is entirely software-based and has nothing to do with the networking side of my current company.
It's disappointing that I wasted a PTO day and there's no compensation from HeadSpin. I was brought in for a role I had no interest in, and they continued the interview/wasting my time regardless; I suppose I should have simply gotten up and left, but I'm a bit too respectful.
I caution you to make sure there is a clear understanding of what role you're interviewing for before wasting a day. I don't think HeadSpin's current hiring/interviewing process allows for that right now.