[kdkeyser]

Did you consider using an B-epsilon-tree [1] ? This is a B-tree, but each node has a staging area for new writes. In practice, incoming writes get added to the staging area of the root node, and once a staging area is full, it gets propagated down. This results in write performance that is similar to append-only. For reads, you get the performance of a regular B-tree. Sounds like a good match for your use case.

[1] http://supertech.csail.mit.edu/papers/BenderFaJa15.pdf

[bluestreak]

I have not had any experience with these trees, but I will try to read and make sense of this paper, thanks! There is C++ implementation here is someone else is interested: https://github.com/rahulyesantharao/b-epsilon-tree