Scalable Multi-Versioning Ordered Key-Value Stores with Persistent Memory Support

Ordered key-value stores (or sorted maps/dictionaries) are a fundamental building block in a large variety of both sequential and parallel/distributed algorithms. However, most state-of-art approaches are either based on ephemeral in-memory representations that are difficult to persist and/or not scalable enough under concurrent access (e.g., red-black trees, skip lists), and/or not lightweight enough (e.g. database engines). Furthermore, there is an increasing need to provide versioning support, which is needed in a variety of scenarios: introspection, provenance tracking, revisiting previous intermediate results. To address these challenges, we propose a new lightweight dictionary data structure that simultaneously provides support for multi-versioning, persistency and scalability under concurrent access. We demonstrate its effectiveness through a series of experiments, in which it outperforms several state-of-art approaches, both in terms of vertical and horizontal scalability.