The source code for the benchmarks is here: https://github.com/the-benchmarker/web-frameworks
And the httpbeast code is here: https://github.com/the-benchmarker/web-frameworks/tree/maste...
TechEmpower and TheBenchmarker are 2 different benchmarks and I'm not sure how they compare.
Besides that benchmarks rarely benchmark realistic code and the Nim blog doesn't mention being the fastest out there, but it mentions "native performance" which I feel like is a fair claim.