Change effective on 24 September 2015
The new Performance-L dynos are a massive upgrade over PX dynos and at the same price point. By default, Node.js apps have a
WEB_CONCURRENCY environment variable suggesting the number of workers to run in a node cluster. That number has just been upgraded from 12 to 28 to take advantage of the cpu, disk, and memory bump. While the default recommendation is a good place to start, you should test your specific app to see what level of concurrency is best.