I came back from a 2-year career gap and Moderna was genuinely one of the more thoughtful places I interviewed at this cycle. Wanted to write up the behavioral round in detail because a lot of what I found online was generic.
Moderna publicly talks about their values a lot: curiosity, urgency, excellence, humility, teamwork. The behavioral round (45 minutes, two interviewers) was explicitly mapped to these. The interviewers told me upfront that they'd be scoring against those pillars.
Questions I got: "Tell me about a time you had to learn something entirely new under time pressure. What did you do and what was the outcome?" (Curiosity + urgency) "Describe a situation where you disagreed with a team decision. How did you handle it?" (Humility + teamwork) "Give me an example of holding yourself to a high standard when nobody was watching." (Excellence) "Tell me about a time you had to communicate a technical problem to a non-technical stakeholder during a crisis." (Teamwork + communication)
Notably absent: questions about failure or things you'd do differently. Usually I expect at least one of those. Maybe they came from a different angle on the "humility" question above.
What worked for me: I used STAR but I kept each answer to about 3 minutes max. I watched the interviewers' body language and stopped when it seemed like they'd gotten what they needed. Moderna is a fast-paced environment by biotech standards (they built a vaccine in less than a year, that's their brand), so I tried to show urgency and decisiveness in my stories, not just thoughtfulness.
One of the interviewers asked a follow-up after nearly every answer, usually drilling into what specifically I did personally vs. what the team did. Own your contribution clearly.
The values/culture round at the end of the loop was with a senior engineer rather than HR. It covered similar territory but with more peer-level conversation, less structured scoring.
I got an offer. The behavioral round was the one I felt most prepared for after practicing STAR stories out loud, which I genuinely didn't do enough in my earlier searches years ago. Makes a real difference.