Around early 2015, Uber’s now deprecated tool for application-layer sharding, called Ringpop, incorporated Riak for high availability.

Ringpop was “a library that brings cooperation and coordination to distributed applications,” which they used, “to build scalable and fault tolerant systems for real-time dispatching by leveraging its sharding capabilities.”

Riak was used as a persistent data store for a portion of the new dispatching services. For example, as objects requiring persistence were generated, such as a new driver coming online with their associated mailbox of potential trips, Ringop would store these IDs as keys within Riak.

These layers could be utilized for additional services, such as stateful HTTP long-poll services, client/server sync services, rate limiters and geospatial services.