Define a Composite Index: Configure a composite index that includes the properties in your WHERE and AND clauses. The order of the properties in the composite index definition should generally match the order in your query's clauses to be most effective.
Note:
To optimize an Azure Cosmos DB for NoSQL query using a composite index, your index definition must precisely align with the properties and sequence of your filters.
For example, an order details container, consider this example query:
SELECT *
FROM c
WHERE c.customerId = "C123" AND c.orderStatus = "Shipped"
ORDER BY c.orderDate DESC
Effective Composite Index Design
To ensure the query is served by the index rather than a scan, your index should follow these rules:
Sequence Matters: The properties in your composite index must appear in the exact order they are used in the WHERE and ORDER BY clauses.
Filter Logic: Include all properties used in your WHERE filters (joined by AND).
Sort Integration: If you have an ORDER BY clause, those properties must come after the equality filters in the index definition.
Order Match: The ascending/descending order in the index definition must match the query for multiple-property sorting.
Example Index Definition:
Property 1: /customerId (Ascending)
Property 2: /orderStatus (Ascending)
Property 3: /orderDate (Descending)
Reference:
https://oneuptime.com/blog/post/2026-02-02-keyset-pagination/view

When using a Copy activity in an Azure Data Factory pipeline to ingest data into an Azure Cosmos DB for NoSQL container, the activity is able to execute two distinct write behaviors (operations): Insert and Upsert.
Write Operations Supported
Insert: This operation acts as a standard append. It attempts to add the incoming data as a new document inside the Cosmos DB container. If a document with the exact same unique identifier (id) already exists in the container, the operation will fail with a primary key conflict error.
Upsert: This operation conditionally updates or inserts data. If an incoming document shares the same id as an existing document in the container, the Copy activity will overwrite (update) the existing document. If the id does not match any existing documents, it will create (insert) a brand new document.
Reference:
https://learn.microsoft.com/en-us/fabric/data-factory/connector-azure-cosmosdb-for-nosql-copy-activity

Instead configure an Azure Monitor alert to trigger the function.
You can set up alerts from the Azure Cosmos DB pane or the Azure Monitor service in the Azure portal.
Reference:
https://docs.microsoft.com/en-us/azure/cosmos-db/create-alerts