And I sit here kind of shocked that Apple would use Java for anything, backend or not. I thought Apple had a strong preference for owning its own tech stacks, whether that be ObjC/WebObjects or later Swift...
Apple's server stack has been primarily Java for about 20 years.
Great use case for Go though, especially its concurrency features for web crawlers. I reckon Scala could work too, although it's a lot more complicated / clever.