MongoDB Atlas + Vercel Serverless: Data Consistency Issues

[zangse]

Having strange behavior with MongoDB operations in Vercel Serverless functions. These issues only occur in production (Vercel live), not in local development with vercel dev.

Issue 1: Cursor Missing After Complex Operations

After successful transaction operations across multiple collections, subsequent queries fail with:
MongoUnexpectedServerResponseError: BSON element "cursor" is missing

Code structure:

// Transaction succeeds
await session.withTransaction(async () => {
  await collection1.updateOne(...);
  await collection2.insertOne(...);
});

// But next query fails
const result = await collection3.findOne(...); // Cursor error here

Issue 2: Response Contamination

After the cursor error occurs, a completely unrelated subsequent request returns data from the failed request instead of its own query results.
Example:

Request A fails with cursor error (should return user data)
Request B querying a different collection unexpectedly returns user data from Request A

Environment:

Vercel Serverless (Production)
MongoDB Atlas
Node MongoDB Driver 6.10.0
Works fine in local development with vercel dev

Questions:

1. What causes cursor state to persist between serverless function invocations in production but not locally?
2. How to properly isolate MongoDB operations in serverless production context?
3. Best practices for connection/cursor management with this stack?
4. Why do these issues only manifest in production environment?

Any help appreciated!

Acknowledgement

• I acknowledge that this discussion will be automatically closed.

[github-actions[bot]]

This discussion was automatically closed because the community moved to vercel.community