You can help to build an evolutionary, accumulate-only database system for modern hardware called SirixDB.

The core repository (Java and Kotlin):

"We want to research the indexing of data in a huge persistent data-structure, mapped to persistent storage. SirixDB stores data and indexes of database resources in a huge persistent tree of tries. It allows us to retrieve any past revision and the current revision, whereas the revisions itself are indexed. The system supports time travel queries, reconstruction of any past state, and to revert to any past state. It only ever aggregates data over time and never overwrites data."

The query processor:

"With our research, we want to develop an extensible, retargetable compilation, and runtime framework for driving scripting-like query languages for structured and semi-structured data. Ideally, we envision to prepare the ground for a tool for query languages similar to what the LLVM compiler framework is for general programming languages: an ecosystem in which proven optimization techniques and algorithms are readily available for implementing custom query processing systems."

The frontend:

"We want to explore how to visualize time-travel queries best and how best to depict the differences between two revisions or any subtrees."