How would you design security for something like Stripe?

"I first cleared the loop for a different Meta EM role and, while I was waiting in team matching, they opened an M1 security role and asked me to do the delta interviews for that. For the security path, the structure was recruiter screen, two technical screens, and then a six-round final loop covering security system design, security depth, coding, career motivation, people management, and project retrospective. The technical rounds were not the hardest part for me because the coding was pretty easy and the design rounds were very framework-driven. The rounds that mattered most were people management and project retrospective, and I actually got more push there because the examples had to map cleanly to the signal. I cleared the loop, and am waiting on next steps."