Walk me through a system you designed and implemented.

"I did a recruiter screen, then a system design screen, then a final loop with three rounds. The surprising part was how system-design-heavy it was: three of the four real interviews were design, and all of them were centered on finance-flavored distributed systems. The design rounds were open ended, but the interviewers were assertive and kept steering back to concurrency, failure handling, atomicity, and resiliency. One final round was a reverse system design where I had to present something I had built before and defend choices like webhooks versus pub/sub, caching, and database tradeoffs. The coding round was still hard, but it felt more like a practical graph or scheduling problem with a twist than a clean LeetCode question. I didn't get the offer, but the process made it very clear that they care a lot more about how you think through real systems than memorized coding patterns."