Modernizing Medicaid Enterprise Systems (MES) involves integrating new modules and building a robust, agile data infrastructure to connect them all and satisfy reporting and operational needs. An MES data infrastructure connects and enables all modules—ideally starting at the evaluation and procurement phase – and evolving to knit them together into a system of systems. This talk discusses how and why to set up data processing as its own workstream in an Operational Data Store, early, rather than as a secondary or just-in-time activity while integrating modules. A modern, agile, flexible data infrastructure, with a powerful ODS, done right and done first, avoids a number of pitfalls seen in various state efforts. We will cover actual pitfalls and outline principles that help prevent them.