This statement is definitely wrong in this generic blank fashion. Also I would lay upon you the burden of proof for it :). Tight, low level code in Java and Go

This statement is definitely wrong in this generic blank fashion. Also I would lay upon you the burden of proof for it :). Tight, low level code in Java and Go is roughly as fast as average C code. The Go compiler is know to be less good at optimizing code than e.g. GCC, but this in many cases creates little practical difference, while the Java JIT compilers have become excellent to a point where they often beat GCC, especially as they can use run time profiling for code optimization. So they can optimize the code for the actual task at hand. Where the languages differ in "speed" is their runtime environment. Java and Go are languages with garbage collection, which of course means that some amount of CPU is required to perform GC. But as the modern garbage collectors run in parallel with the program, this CPU effort often enough is no bottleneck. On the other side, manual memory management has different performance trade-offs, which in many cases can make it quite slow on its own.