This article focuses on a multiple source prioritization and validation service. We describe a modern rule-based, loosely coupled solution. We follow generalization, efficiency and agility principles in application design. We show benefits and stumbling blocks in micro-service architectural style and in rule-based solutions, where even the selection task is solved through selection rules, which encapsulate the calls to Entity Services, allowing access to input-sources. We allowing the rule-based service efficiency and further local and remote input data selection scenarios for the validation Statistical Service. In particular, data virtualization technologies enable architects to use remote sourcing and further increases agility in data selection issues. Through a wide number of experimental results, we show the necessary level of attention in process implementation, data architectures and resource usage. Agility and efficiency emerge as drivers which possibly sustain the Modernization flexibility impetus. In fact, flexible services may potentially serve multiple scenarios and domains.