A multi-tenant app filters nearly every query by tenantId. Which partition key choice minimises RU cost?
- A /id
- B /tenantId (correct answer)
- C /createdDate
- D A synthetic key of /type-/region
Shortcut: Partitioning by tenantId makes those filtered queries single-partition, which is the cheapest access pattern. /id would spread a tenant's documents across every partition, forcing fan-out.