[mrkeen]

> how do you know if the inner list changed or not

This is a vital question that virtually every programming language overlooks.

If you are using a mainstream language, you do not know if they were modified.

If you use a language which has a type system to segregate mutable operations from immutable operations, then you know if they were modified.

> They work in the small, but don't truly scale.

Go even bigger then. Work with the kind of data that won't fit in memory. Put your data on disk - you can't insert into the middle of a 1GB+ file.