What is GraphQL? The draft RFC specification (October 2016), defines it as "a query language created by Facebook in 2012 for describing the capabilities and requirements of data models for client‐server applications". More simply, GraphQL is a language specification for API. It defines in which way the client should query the server, and in which way the server should execute those queries.
Scala is general purpose programming language very popular for building web application. But why? At the moment I really don't know why :) , I'm just reading about it and sharing my thoughts with you.
Let's start from Scala. It's a programming language both object-oriented and functional: we can refer to this kind of programming language as "object-functional". We say that is a programming language because there is a compiler for it, but also an interpreter is available.
It is intended to be compiled to Java bytecode, so the resulting executable runs on the JVM, and Java libraries can be used directly in Scala code and vice-versa. Maybe this is the real strength of this language... it allows to write brand-new web application while reusing legacy java libraries. That's awesome for a company with a bunch of old java code.