Analyze a hypothetical monolithic e-commerce backend written in Java. Propose a domain-driven design approach to break it down into microservices. Specifically, define the bounded contexts for Inventory, User Management, and Order Processing. Discuss the data consistency patterns you would implement (e.g., Saga pattern) and explain how to handle inter-service communication synchronously vs. asynchronously. Provide a high-level sequence diagram for the 'Checkout' process.