What feature detects new or updated items in Cosmos DB for downstream work?
Why C is the answer
The change feed
The change feed exposes changes, and a change feed processor reacts to them.
In detail
- The change feed reports new and updated items.
- It avoids scanning whole containers.
Use case
An illustrative scenario, not a real incident.
An order system must update search when items change. The change feed reports each new or updated item.
See it in different ways
sequenceDiagram participant A as App participant C as Cosmos DB participant P as Change feed processor participant E as Embedding model A->>C: Create or update item C-->>P: Change P->>E: Text E-->>P: Embedding P->>C: Save the embedding
sequenceDiagram participant C as Cosmos DB participant P as Change feed processor participant M as Embedding model C->>P: New or updated item P->>M: Text M-->>P: Embedding P->>C: Stores the vector
flowchart LR S0["Write"] --> S1["Change feed"] --> S2["Downstream work"]
Key point: The change feed detects changes.
Why the other options are wrong
- A. Partition key rotation
- Partition keys do not rotate.
- B. The indexing policy on the container
- The indexing policy controls indexes.
- D. A scheduled full scan of every container each minute
- Full scans are costly.