Very unprofessional. I ended up spending an hour on HackerRank, then up to 7 one-hour sessions on Zoom, only to end up with no follow up. Here's is a quick rundown of my experience:
1. CTO reaches out to me and we eventually have an introductory call
2. Solve two problems on a one-hour session at HackerRank
3. Technical interview with a software engineer
4. Technical interview with another software engineer
5. Meet with a product manager
6. Meet with CTO, again
7. Meet with VP of Product
8. Meet with CEO
9. Meet with COO, also co-founder
This all happened in a span of about 5 weeks. However, they just flat out ghosted me after the last meet with the COO. No follow up email, nor phone call. Obviously, they don't want to extend an offer by now, but I think a one-sentence email would've been nice.