Change feed: change feed processor with a lease container, Azure Functions Cosmos DB trigger, latest-version mode vs all versions and deletes

The change feed is a persistent, ordered record of changes to items in a Cosmos DB container. Instead of polling with queries, your code reads what changed since it last looked. It is the backbone of event-driven patterns: updating a search or vector index when documents change, generating embeddings for new items, keeping a cache or a materialized view in sync, or triggering workflows. Changes are ordered within each partition key value, but not across partitions.