Like concurrency and parallelism, scalability and performance are not the same thing.
"The terms "performance" and "scalability" are commonly used interchangeably, but the two are distinct: performance measures the speed with which a single request can be executed, while scalability measures the ability of a request to maintain its performance under increasing load. For example, the performance of a request may be reported as generating a valid response within three seconds, but the scalability of the request measures the request's ability to maintain that three-second response time as the user load increases."
|--Pro Java EE 5, Steve Haines|
It is not unusual for a reviewer to assert that Node cannot scale across cores and is, therefore, unable to optimize performance on a given machine. This belief is based on two false impressions—that Node is "not good at" CPU-intensive tasks and that it cannot scale because its process can only leverage a single core. These claims...