Did the full loop for a senior SWE role at Notion earlier this year. Sharing the system design piece since I couldn't find much on it before I went in.
Notion doesn't have public level names the way Google does with L3-L8, but from what I can tell they map roughly to something like senior = "L5 equivalent" at the bigger companies. The recruiter confirmed I was interviewing at the senior level, which meant the system design round was weighted more heavily than the coding.
The format. 60 minutes, 1:1 with a senior or staff eng. No whiteboard (all remote), they use a shared doc. First 5-10 minutes is intro and some light scoping questions about your background. Then the actual design prompt.
What they asked me. I got a prompt roughly like: design a collaborative document editing system that supports real-time sync across multiple users. Which, yes, is basically "design Notion." I don't know if that's always the prompt or if I got lucky/unlucky depending on how you feel about that.
The conversation stayed at the architectural level. They cared a lot about: How you handle conflicts when two users edit the same block simultaneously (operational transforms vs. CRDTs came up) Your data model for a block-based document structure How you'd approach the sync layer (WebSockets, polling fallback, what happens offline) Scaling: how does your design hold up at millions of concurrent users vs. thousands
They didn't push deep into implementation details. It felt more like a product + systems conversation than a pure distributed systems grind. The interviewer was clearly curious whether I'd thought about the tradeoffs, not whether I'd memorized a textbook.
What I wish I'd done differently. I spent too long on the data model and didn't leave enough time for the scaling conversation. I also didn't proactively mention offline-first behavior early enough. That seemed like something they care about given the product.
Overall a solid round. Not FAANG-hard but not trivially easy either. The OT/CRDT question will separate people who've thought about it from people who haven't.