You are designing a Cosmos DB container for a logistics platform that stores shipment events. Each shipment belongs to a specific carrier, and there are only 8 carriers. Within a carrier, events are queried almost exclusively by shipmentId. The largest carrier will generate roughly 400 GB of event data over the container's lifetime. Most read queries filter by both carrierId and shipmentId, while a nightly report scans all events for a single carrier. Which partitioning strategy best balances query efficiency and avoids exceeding logical partition limits?