Node's goal is to provide an easy way to build scalable network programs. In the "hello world" web server example above, many client connections can be handled concurrently. Node tells the operating system (through epoll, kqueue, /dev/poll, or select) that it should be notified when a new connection is made, and then it goes to sleep. If someone new connects, then it executes the callback. Each connection is only a small heap allocation.

This is in contrast to today's more common concurrency model where OS threads are employed. Thread-based networking is relatively inefficient and very difficult to use. See: this, this, and this. Node will show much better memory efficiency under high-loads than systems which allocate 2mb thread stacks for each connection. Furthermore, users of Node are free from worries of dead-locking the process—there are no locks.

The Walkable and Livable Communities Institute is a nonprofit center based in Port Townsend, Washington.  Our mission is to make cities and towns throughout the world walkable, bicycle and transit friendly, livable, sustainable, socially engaging and welcoming places by improving their built form. It is challenging to have good health when our environments do not support us.

Walkable communities are thriving, livable, sustainable places that give their residents safe transportation choices and improved quality of life. Walkable Communities, in partnership with the Walkable and Livable Communities Institute, Inc., (www.walklive.org) helps them get there.