You're a PM at Meta. How would you measure the success of Facebook's notification bell and its drop-down menu?

"I interviewed in late January for an L5 PM role on Meta's AI track, and the recruiter straight up told me the process had changed the week before. I first did a traditional product sense screen and a traditional analytical screen, then there was a pause while they reviewed those before deciding whether to give me an intermediate AI product sense round. That AI round was the unusual part: about 30 minutes of normal product sense and then a switch into Meta's Llama tool to vibe code a prototype live. It felt like I was one of the early guinea pigs because even the interviewer seemed to be figuring out the format in real time. I got tripped up by technical follow-ups on latency, token usage, retrieval, and compute, and I didn't make it to the final loop."