Act as a Senior Solutions Architect. Design a high-frequency trading platform architecture using an event-driven microservices approach. The system must handle 100k transactions per second with sub-millisecond latency. Address the following in your response: 1) Partitioning strategy for the event stream (e.g., Kafka topics), 2) Data consistency models (CQRS vs. Saga pattern), 3) Circuit breaker patterns for fault tolerance, 4) Strategy for handling out-of-order messages, and 5) Infrastructure requirements for multi-region deployment with active-active geo-redundancy. Provide a detailed diagram description and a justification for your technology stack choices.