There are definitely problems on both end of the scale, but I’m seeing more of the former definitely - I think it depends a lot on what kind of environment you’

There are definitely problems on both end of the scale, but I’m seeing more of the former definitely - I think it depends a lot on what kind of environment you’re in. I more often encounter people using “premature optimisation” to not do any optimisation at all. It results in applications that have a much lower performance ceiling and more often require a rewrite relatively soon. Edit: I also want to add that in this specific case with Java, using functional interfaces with primitive datastructures often doesn’t really have any downside. If you know you need to filter the data to a lower scale first before continuing (e.g. to the amount you can display on one page), it’s just not sensible to object box your entire data first, just so you can avoid having arrays anywhere in your code. Just have a class for your data and expose some rich interfaces to it, but implement paging on top of primitive data in this case.