Static arrays as in constant fixed sized arrays. With a static array, O(N) is faster than O(LogN) and even some cases O(1) ahem, hashes when N is small. A contiguous cache is king, and even with modern dynamic languages, the generational GC can even be completely bypassed or highly simplified if the JIT learns that memory access is just dependent on offsets.

Simple code runs fast.

See Pike on Complexity - Rule 3: https://www.lysator.liu.se/c/pikestyle.html