Mathematica is extremely performant for most of the built-ins, the overhead of interpretation is nearly negligible for all but the tiniest operations. There is

Mathematica is extremely performant for most of the built-ins, the overhead of interpretation is nearly negligible for all but the tiniest operations. There is also no reason to think that their request-response boilerplate is written in Mathematica, Mathematica is fully integrated with a lot of languages and runtimes.