You might enjoy a paper I’m a coauthor on which combines finger trees with B-trees to build a data structure for optimal updates to sliding windows: Optimal and General Out-of-Order Sliding-Window Aggregation, https://www.scott-a-s.com/files/vldb2019_fiba.pdf
Slides from the conference talk: https://www.scott-a-s.com/files/vldb2019_fiba_slides.pdf