Using Transaction for signup, in express/mongoose

[Shamsmedhat]

Hi everyone,

I’m a junior backend developer working with Node.js.
While working on my app, I made a typo in process.env and noticed that a user was still being created even though the token was not generated successfully.

I understand why this happened technically, but from a business-logic perspective, this flow doesn’t feel correct. A user should not be created if their token generation fails.

After some research, I found that one possible solution is to use a database transaction to ensure that both operations creating the user and generating the token either succeed together or fail together.
This way, the signup process remains consistent and reliable.

My question is: Is using a transaction the best approach for this case, or are there other recommended patterns or solutions that I might be missing?

Thanks!

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[ohhaus]

Yes, using a database transaction is the correct and professional approach for this problem. Your solution is exactly how this should be handled in a production backend.

Your reasoning is sound from a business logic perspective. The signup process is a single atomic operation: both the user record creation and the token generation must succeed, or neither should happen. Your transactional implementation ensures this data consistency.

Key Strengths of Your Transaction Code:
Atomicity Guaranteed: The session.commitTransaction() only happens if both operations succeed. If the JWT signing fails, session.abortTransaction() prevents the user from being persisted, leaving no orphaned records.

Proper Cleanup: The finally block ensures the session always ends, preventing connection leaks.

Correct Data Access: You correctly access the created user as newUser[0] since Model.create() with a session returns an array.

Complementary Best Practices:
While transactions solve the core problem, adopt these patterns for a more robust system:

Environment Validation: Validate critical process.env variables (like JWT_SECRET) when your app starts, not at runtime. Use a library like envalid.

Structured Error Handling: In your catch block, log the error and throw a specific, user-friendly AppError instead of a raw database error.

Idempotency Consideration: For network retries, consider adding a unique idempotency key (like a UUID from the client) to prevent duplicate user creation from identical repeated requests.

Your implementation shows good understanding. The transaction pattern you've used is the standard solution for this class of problems.

[Shamsmedhat]

Thanks a lot! For your feedback, really appreciate 🙏