Question

Your team built an Azure Function with a Cosmos DB trigger to process the change feed of an 'Orders' container for real-time fraud scoring. During a marketing campaign, order volume increases tenfold. You observe that a single Function instance is processing all changes and cannot keep up, causing rising latency. The container has 20 physical partitions. What is the correct way to enable the Function to scale out and process changes in parallel across multiple instances?

Accepted Answer

Ensure a lease container is configured for the trigger; the Consumption plan will automatically scale out Function instances, distributing partition key ranges (leases) across them.

Answer

Increase the MaxItemsPerInvocation setting so a single instance reads larger batches, which removes the need for additional instances.

Answer

Switch the Cosmos DB account to multi-region writes so each region's Function app processes a subset of the change feed independently.

Answer

Manually create 20 separate Function apps, one per physical partition, and hard-code each to poll a specific partition key range.