Applied cold via the website. Heard back in about 8 days, which felt fast. Here's the structure I went through:
Round 1: 30-min recruiter screen. Pretty standard, focused on motivation and timeline. She was direct and asked me to be direct too, which I appreciated.
Round 2: Technical with a senior ML eng. Not a leetcode grind. They gave me a real problem: design a ranking system for search results that handles freshness vs. relevance tradeoffs. Open-ended. They wanted me to reason through it, not solve it perfectly. I spent the first 15 min asking clarifying questions and they seemed to like that.
Round 3: Systems design + product intuition hybrid. This was the unusual one. Half was infra (how do you build low-latency retrieval at scale), half was basically "what would you change about how Perplexity answers this type of query." They want people who are users of the product, not just builders.
Round 4: Brief culture/values chat with someone on the leadership team. Light but not perfunctory. They probed for how I handle disagreement.
Total: 3.5 weeks from application to offer. Offer turnaround was 4 days after the last round. They do move fast.
One thing that surprised me: they explicitly said they were NOT looking for people who needed a lot of process overhead. If you need a lot of consensus before shipping, probably not the fit.