A recruiter reached out to me about this position. I applied, then there was an initial call, after which I was invited to do the coding collaboration.

The coding collaboration is with two engineers, and you have to find the bug in the code and fix it. I successfully completed the task and even optimized the code. I left the interview knowing I did a great job.

However, I was rejected in the most polite way: they told me how impressed they were with my skillset but decided not to move forward. I asked for feedback on the interview and was ghosted.

As noted here, candidates have to sign an NDA.

Essentially, you are given code for a real-world problem, and you have to find and fix the bug.

Be familiar with HTTP servers and clients, as well as basic SQL commands.