The NodeJS cluster module can be used to do load balancing between multiple processes on the same machine - It supports load balancing either at the OS level or

The NodeJS cluster module can be used to do load balancing between multiple processes on the same machine - It supports load balancing either at the OS level or at the application level. The application level 'round robin' approach is the default and leads to more even distribution between processes in terms of CPU usage. The application 'round robin' approach may be limited in terms of scalability at some point but I've done tests with 32 processes on a 32 core machine and I couldn't see the slightest sign of struggle from the process which hands off the connections to worker processes. Hopefully, eventually the OS scheduler in Linux will have improved enough to outperform the application-level LB but for now it hasn't. In any case, you don't necessarily need loadbalancing at the host level, you can load balance at the cluster level only. Your load balancers (e. g. nginx or haproxy...) have their own hosts/machines in your cluster and they loadbalance between processes directly. Some of those may be running on the same machine but the load balancer does not dostinguish between them. A random load balancing approach yields the most even distribution from my experience - You do need each process to be able to support maybe 1k concurrent users in order to get the sample sizes on each prpcess to allow even random distribution between them but this is easily achieved with most Node.js WebSocket libraries. They can easily support 10K concurrencr connections per prpcess with very high message throughput. If the commections are mostly idle, each process can handle 100k connections or more.