I like Node.js' simple and fully isolated concurrency model. You shouldn't be blocking the main event loop for 30 seconds! The main event loop is not intended to be used for heavy processing.

You can just set up a separate child process for that. The main event loop which handles connections should just co-ordinate and delegate work to other programs and processes. It can await for them to complete asynchronously; that way the event loop is not blocked.

I recall people have been able to get up to around a million (idle) WebSocket connections handled by a single process.

I was able to comfortably get 20k concurrent sockets per process each churning out 1 outbound message every 3 to 5 seconds (randomized to spread out the load).

It is a good thing that Node.js forces developers to think about this because most other engines which try to hide this complexity tend to impose a significant hidden cost on the server in the form of context switching... With Node.js, there is no such cost, your process can basically have a whole CPU core for itself and it can orchestrate other processes in a maximally efficient way if you write your code correctly... Which Node.js makes very easy to do. Spawning child processes and communicating with them in Node.js is a breeze.