Act as a Senior Solutions Architect. Design a scalability strategy for a microservices-based e-commerce platform currently handling 10,000 requests per second (RPS) with a target of 100,000 RPS. Your strategy must address: 1) Database sharding and replication topology for PostgreSQL, 2) Caching layers using Redis for session and product data, 3) Message queuing mechanisms (e.g., Kafka vs. RabbitMQ) for asynchronous order processing, 4) Auto-scaling policies for Kubernetes pods based on custom metrics, and 5) A Circuit Breaker pattern implementation to prevent cascading failures. Provide a detailed technical explanation, including potential trade-offs for each decision.