Act as a Senior Solutions Architect. Design a high-level architecture for a global e-commerce platform expected to handle 50,000 concurrent users. Your design must include: 1) A microservices breakdown structure. 2) Database selection strategy (SQL vs. NoSQL) per service with justification. 3) Caching layers and eviction policies. 4) An asynchronous message bus for inter-service communication. 5) Circuit breaker patterns to prevent cascading failures. Explain the trade-offs involved in your CAP theorem choices.