What is a stored procedure in Cosmos DB and what are its limitations?

Stored procedures in Cosmos DB are JavaScript functions registered on a container and executed server-side on the Cosmos DB engine itself. They run atomically within a single partition — meaning all operations inside the stored procedure either all commit or all roll back, giving you ACID transaction semantics without distributed coordination overhead.

A stored procedure is registered and then called via the SDK or REST API:

// Register a stored procedure
const sprocBody = function createDocIfAbsent(id, body) {
  var context = getContext();
  var collection = context.getCollection();
  var response = context.getResponse();

  var query = { query: "SELECT * FROM c WHERE c.id = @id", parameters: [{ name: "@id", value: id }] };
  var isAccepted = collection.queryDocuments(collection.getSelfLink(), query, {}, function(err, docs) {
    if (err) throw err;
    if (docs.length > 0) {
      response.setBody(docs[0]);
    } else {
      var accepted = collection.createDocument(collection.getSelfLink(), body, function(err, doc) {
        if (err) throw err;
        response.setBody(doc);
      });
      if (!accepted) throw new Error("createDocument not accepted");
    }
  });
  if (!isAccepted) throw new Error("queryDocuments not accepted");
};

await container.scripts.storedProcedures.create({ id: "createIfAbsent", body: sprocBody });

// Execute it
const result = await container.scripts.storedProcedure("createIfAbsent").execute(partitionKey, [id, body]);

Key limitations to know for interviews:

• Single partition scope only — A stored procedure cannot touch items across multiple partition key values. All reads and writes must target the same logical partition passed at invocation time.
• Continuation token required for large result sets — Stored procedures have a time and response size budget. If a bulk operation does not complete in one execution, you must implement pagination using continuation tokens and re-invoke the procedure.
• No external HTTP calls — Server-side scripts cannot call external APIs or Azure services. Logic must be pure JS within the Cosmos DB context API.
• JavaScript only — No other language is supported for stored procedures, triggers, or user-defined functions.