WorldCat is the world’s largest network of library content and services. Over 25,000 libraries in 170 countries have cooperated for 40 years to build WorldCat. OCLC is currently in the process of transitioning Worldcat from Oracle to Apache HBase. This session will discuss our data design for representing the constantly changing ownership information for thousands of libraries (billions of data points, millions of daily updates) and our plans for how we’re managing HBase in an environment that is equal parts end user facing and batch.