[Uchikoma]

We run a major site on Java, had some thread trouble years ago in the very beginning, works very well now when tuned. Threads work.

BUT: I assume people will move to backend services with REST and combining REST backend results to a page. This increases IO a lot and will kill your latency and default thread models when you do sync code. You'd need to use async IO, composeable futures to manage latency and thread count. And if you do async backend REST, why not do async JDBC etc. But there are no libraries.