If you have an array of small structures, all you have to do is access all of them in one go with a for() loop and you're already taking advantage of the cache. This is enforced in ECS frameworks, btw: it's how a "System" is implemented.

However, if your code has random access, there's no point in using arrays of structures. The compiler would have to modify the order of execution of instructions inside your method to take advantage of how the data is laid out.