Have you every written a scheduling app or a booking engine? At their scale, it’s hardly not interesting. Just that aspect alone is crazy hard to get right. On top of that they essentially have a CMS for hosts and very complex payment system. Security alone requires a pretty massive team.

Each component of their system could be a separate company. I own a small B&B in a tiny corner of Provence and I get dozens of inquiries a week — all of those inquires are spending time looking at images, checking availability, etc. now multiple that across almost the world and you will find some extremely interesting engineering challenges.

And site reliability has been exceptional. I’ve also never encountered a single bug in my normal use. That’s a big deal.