A retail company is building a product catalog service. Each product is a flexible document with varying attributes (some have color/size, others have volume/weight), and the mobile app must fetch a single product by its ID with sub-10-millisecond latency and support ad-hoc queries on individual product fields. The catalog has about 5 million products and receives moderate read traffic with occasional single-document updates. There is no requirement for complex multi-table joins or analytical aggregation. Which storage service best fits these requirements?