The short answer is nothing. They create their own problems of scalability by their own poor engineering. Who still uses rails for an api/iphone app these days?

The short answer is nothing. They create their own problems of scalability by their own poor engineering. Who still uses rails for an api/iphone app these days? As far as MySQL being the bottleneck, I'm kind of wondering why that is. I'd imagine 99% of their workload is both cacheable and read only, and thus infinitely scalable. Anyway, I've used Hotel Tonight a few times and most of my experiences with the actual product have been poor. The price I could have got through the hotel directly in a few cases would have been better, and the other time they promised a King bed only to be rebooked at the hotel to a smaller room and double bed. It seems their business model is largely around selling unused inventory at hotels for as high a price they can get, without really caring about the customer. You'll notice they have an absolutely no money back policy. In my case I was forced to take the lesser room which was actually cheaper had I paid for it at the hotel. Since that experience I deleted their app.