I've been through the Plaid process twice now: once as a candidate (a few years back) and once sitting in on panels as a contractor helping with interviewer calibration for a team I was advising. So I've seen both sides of this specific loop, which is unusual.
The behavioral round at Plaid is 45 minutes and structured around what they loosely call core competencies. They're not using STAR explicitly but the interviewers are trained to probe for Situation/Action/Result anyway. If you're used to giving a 90-second story with no depth, expect follow-up questions that force you to go deeper.
Themes I've seen come up consistently:
Ownership under ambiguity. Something like: tell me about a time you had to make a call without all the information you needed. They want to see that you can move forward without perfect data and take real accountability for the outcome.
Cross-functional influence. Plaid is not a siloed org in the traditional big-co sense, but you still work across product, eng, legal (compliance is a real thing in fintech), and external bank partners. Stories about navigating competing priorities across teams land well.
Handling failure. Not softened failure. Real failure. A thing that didn't work, a project that got killed, a technical decision that cost the team. How you diagnosed it, what you changed. They can tell when someone's packaging a minor inconvenience as their "failure story."
On values: they talk publicly about reliability, trust, and the mission around financial access. That's not marketing fluff in the interview context. If your stories connect to why clean, reliable financial data matters for real people, the interviewers respond to it.
Compensation point: behavioral outcomes can affect leveling signals, which affects offer. If you're borderline L4/L5 on technical, strong behavioral can tip it. The reverse is also true.
One thing I tell people: don't save your most honest stories for behavioral. Use the real ones. The ones where you're actually a little uncomfortable retelling them. Those read as authentic.