Just finished and wanted to write this up while it was fresh. Applied for a Senior SWE role on the Payments Processing platform team.
Round 1: Recruiter screen, ~25 min. Standard fit questions, a bit of comp probing. She was upfront that the role was hybrid O'Fallon, not remote, which I appreciated.
Round 2: Technical phone screen with a senior engineer. 45 minutes. Two LeetCode-mediums (arrays/hashmaps, nothing exotic), plus maybe 10 minutes of systems design at the end. She asked me to sketch how I'd handle idempotency in a payment API. Classic, if you've done any fintech work you've thought about this.
Round 3 (Final loop, virtual, 4 panels): System design: design a fraud alert notification system. They wanted to talk about scale, latency tolerance, and what happens when the downstream bank's endpoint is flaky. Coding: two mediums, one of which had a follow-up about time complexity. Nothing fancy. Behavioral x2: both panels heavy on "tell me about a time you influenced a decision without authority" and "cross-functional conflict." This is clearly what they care about.
Total time from application to offer call: 5.5 weeks. Recruiter was responsive and kept me in the loop.
The thing that surprised me: they asked almost nothing about payments domain knowledge. The system design was payments-flavored but they were fine if you reasoned through it from first principles. Don't feel like you need to memorize ISO 8583 or whatever.