The QaFoo blog has written up an interesting post looking at languages and scalability and some of the constraints that can come along with them.

Micro-Services or any set of small services are common again right now. While it can make a lot of sense to use a dedicated service for a well defined problem those services are sometimes used just to play with a different server software. While it is pretty obvious for most that selecting the right database is important the same is true for selecting the right language (virtual machine) for the job.

There are different types of services or server applications where different types of virtual machines (executing the opcodes / bytecode of the compiled source code) make more or less sense. What are the criteria we should base such a decision on and which language should we choose when?

As their primary work is related to PHP, they focus in on it. They talk about why PHP has become such a popular language (the "LCoDC$SS" acronym) and why it fits in with HTTP's statelessness perfectly. On the flip side, they also talk about when it doesn't make sense to use PHP - mostly centering around what would take long-running PHP processes. They then compare this to a similar setup with other languages like Node.js, Go and Java (and how well those scale themselves).