I have experience building PCs with gaming in mind. But where do I start when it comes to building a server (running specifically NodeJS programs)?
I know the most significant factor would be the code itself, but assuming the code is perfect what part matters the most for the quickest code handling? Is it a multi-core processor, is it the memory? Are there dedicated server hardware parts?
It depends on your code structure if your code is very compute intensive then you need multi-core processor if possible many-core . If your code is of more IO then you need to keep in mind the memory factor. The most important is all the hardware must be capable of supporting maximum limit of others (like if processor is on extreme them memory should be sufficient to support processing etc.).
All the benchmarks available are based on the specification like on what factor they measure the performance. The best way is to find a specification . There you find the criteria description that help you to choose the benchmark.
You can start from this link Benchmark Spec and choose that suits your need.