Serious question, isn't think just rebuilding the same thing that commercial cloud pubsub offerings already provide?
What's impressive to me is that they need all that architecture. Mcdonalds sells under 100 burgers a second from what I can find, their order load is probably bursty, so assume maybe all the orders come in the same third of the day, so 300 per second, and every burger is it's own order... that's still not that much.
One order is more than one operation when you're dealing with everything a place at McDonald's scale, but even if you multiply by a factor of 10 to account for analytics, compliance, etc. 3,000 operations per second? Does that really require an entire Kafka-driven event architecture?