Thumbtack Software Developer interview questions

Round 1: Technical skills evaluation. One of the recruiter from company called me. Round 2: Take home test. Round 3: Phone screen(Coding interview). The coding interview was pretty much easy, not so difficult when compared to other start ups

Applied online. Recruiter quickly responded and setup a call where he described the position and I gave my background. The next step was to do the coding challenge - create an in memory DB. They recommend 30mins to 90mins on it, but I spent about 3hours, just being thorough and making sure everything was correct. A week later a technical phone screen was scheduled. Interviewer asked me to describe a technical challenge I had faced, and then asked me to code a solution to a question on a shared document. The question wasn't too difficult. After I coded the solution, he added a few requirements and asked me to code those up. As soon as I got it working, interviewer basically said "Great! Awesome!" and moved on. He never really asked follow up questions or wanted me to discuss my implementation or ways to improve it or anything, I got my rejection email the next day. I was a bit surprised since I felt my solution to the coding question was good and the interviewer seemed fine with it. I didn't receive any feedback on why I was rejected either. I was also a bit frustrated because initial coding challenge that I did was never brought up at all, so I felt like I had kind of wasted some time doing it. I will say that everyone (all the recruiters, coordinators, interviewers) were super nice, and they were efficient and timely in letting me know about their decision.