How would you build a system on a ticketing website to manage high traffic during simultaneous ticket purchases?

"A recruiter cold-reached out to me for an E5 software engineer role, and the whole process felt very standard Meta. I had a short recruiter call, then a coding screen with two common problems in one session, and I actually did poorly on the easy one but still barely made it through. After that I got the full loop spread across multiple days, and they gave me a few weeks to prepare. The final coding rounds were mostly standard too, but I felt weak in behavioral because I did not have the right work stories ready, especially for conflict, and I think I mishandled system design by not controlling time and not setting scale assumptions myself. I got the rejection after the final round."