Comment by Archer6621

If you have an instance (which is what I assume is implied by "real-life data structure") bounded by a particular size, then you could say that the runtime complexity is constant with respect to that bound. Whether that is a useful statement to make is another discussion entirely. On its own probably not. It can potentially be useful for analyzing the runtime complexity of operations in more complex algorithms that use this data structure up to a certain fixed size, e.g. as a buffer/cache of some sort.