I built a project that implemented intervaltree in Rust and exposed PyO3 bindings as a drop-in replacement for Python's native intervaltree. It is significantly faster, and I will be adding more features, such as AVL and red-black trees for balancing.
And with a little work you can even use them to map ranges of keys to values in a way that's reminiscent of interval trees — e.g. https://crates.io/crates/rangemap. (Disclosure: that's my crate.)
Nice! I was only suggesting considering BTrees because they also play nice with caches, instead of the more conventional binary tree balancing mechanisms.