[mistercow]

I feel like there are a number of data structures that you might initially set up (or load in) in some preferred contiguous order, which will still remain largely contiguous after modification, so that you get a good tradeoff between cheap operations and fast traversal. You’d then have the option to do partial defragmentation at convenient times, without having to have a convoluted hybrid data structure. But it’s definitely something you’d do in specific critical cases after a lot of analysis.