Act as a Principal Software Architect. You are tasked with designing the backend architecture for a global social media platform expecting 10 million concurrent users. Your solution must address the following constraints: 1. Strong data consistency is required for financial transactions but eventual consistency is acceptable for feed updates. 2. The system must handle high availability with a tolerance of RPO (Recovery Point Objective) near zero. 3. Latency must remain under 200ms for 99.9% of read requests. Provide a detailed architectural blueprint including: a) The choice of database technologies (SQL vs. NoSQL) and justification for specific data models. b) A sharding strategy to distribute load evenly. c) A caching layer design to reduce database load. d) An explanation of how you handle partition tolerance and network splits within the context of the CAP theorem. e) A disaster recovery plan for multi-region failover.