Act as a Senior Solutions Architect. You are tasked with refactoring a 10-year-old monolithic e-commerce platform written in Java into a scalable microservices architecture. The monolith handles user management, inventory, order processing, and payments. Identify the boundaries for domain-driven design (DDD) contexts, propose a database migration strategy to ensure data consistency during the transition, and define the inter-service communication protocols. Additionally, discuss how to handle authentication and authorization across the new distributed system.