They reached out to me, so if you're an engineer and you've never applied to this company, I'd recommend passing on their interview process. I have a feeling they reach out to candidates so they meet a quota when they already have someone in mind.
Overall, one of the worst interview experiences I've had. This company will waste your time. I spoke with a technical recruiter, then completed a coding challenge. Then I received a standard, bottle rejection. When I asked for feedback, I was given a very vague response. If you expect your candidates to spend a chunk of time on the technical challenge, the least you can do is provide decent feedback. As an engineer who has passed technicals for much more well companies than Solace, it makes me think their hiring process/the company itself is shady.