just finished a senior SWE (P4 equivalent, roughly L5 at other companies) system design round at Atlassian so writing this up while it's fresh.
the round was 60 minutes, one interviewer, and the prompt was broad enough that you had to scope it yourself. mine was something like: design a real-time notification system that works across Jira, Confluence, and Trello. they're clearly pulling from their own product domain, which makes sense.
what they cared about: how you disambiguate requirements before drawing boxes. i spent about 8 minutes asking clarifying questions and they seemed happy with that. scalability reasoning. not just "use kafka" but why, and what the trade-offs are vs. a simpler pub/sub. cross-service fan-out. since the products are separate, this came up naturally. think about deduplication across consumers. your comfort with eventual consistency vs. strong consistency trade-offs at scale.
i didn't get a single leetcode-style trick. this was pure distributed systems design the whole way. no trick question at the end.
time split roughly: requirements: 8-10 min high-level architecture: 15 min deep dive on one component (i chose the fan-out layer): 20 min what would break at 10x load: 10 min questions: 5 min
leveling note: they told me upfront that P4 at Atlassian is typically someone with 5-8 YOE who can drive a system from ambiguity to design without much hand-holding. if you need the interviewer to suggest the next step, that's probably a P3 signal.
i'm a backend eng with 9 YOE mostly in distributed systems so this played well for me. if you're more frontend-heavy, i'd ask the recruiter whether the design round is infra-flavored or product-architecture-flavored. they do adjust.