Act as a Principal System Architect. Design a microservices architecture for a global real-time messaging application handling 10 million concurrent connections. Your response must include: 1. A high-level component diagram description. 2. Database schema selection strategy (SQL vs NoSQL) and justification. 3. Message broker choice and data partitioning strategy. 4. A plan for handling eventual consistency across geographically distributed regions. 5. Rate limiting and DDoS mitigation strategies. Ensure the design prioritizes low latency and high availability.