Question

An e-commerce team stores orders in a Cosmos DB container partitioned by /customerId. A separate reporting service needs a continuously updated materialized view aggregating daily sales totals per product into a second container partitioned by /productId. The team wants a low-latency, resilient mechanism that reacts to each new or updated order without polling or scheduled full scans. Which approach should they implement?

Accepted Answer

Use the Azure Cosmos DB change feed (via the change feed processor or an Azure Function trigger) to read order changes and write aggregates to the product container.

Answer

Create a post-trigger on the orders container that writes to the product container within the same operation.

Answer

Schedule a nightly cross-partition query with the SDK to scan all orders and rebuild the product aggregates.

Answer

Enable a stored procedure that runs on a timer to aggregate orders and upsert into the product container.