The CollectionIncarnationSnapshot will acquire a consistent, static view of the collection incarnations corresponding to all requested namespaces early on in the root router of a query operation. It should:

• Produce a static mapping between a list of required namespaces and their collection incarnations.
• Be compatible with the RoutingContext, as it will be passed in to validate that the RoutingContext only requests namespaces that already exist in the CollectionIncarnationSnapshot.