MERN Inventory Stock API Enhancement

I already have a full MERN-based clothing store in production, but the backend APIs that track inventory are still too basic. Right now each purchase simply decrements a number in MongoDB; I need a more reliable, flexible system for stock-level updates that can handle concurrent orders, returns, manual admin edits, and future integrations with external warehouses.

Here’s what I’m looking for:

• New or refactored Express endpoints that receive real-time stock changes (sale, refund, restock) and update MongoDB atomically so overselling can’t occur.
• A background job or change stream to reconcile discrepancies and alert me when stock hits safety thresholds.
• Middleware to log every adjustment with the user ID or service that triggered it for audit purposes.
• Integration tests (Jest or similar) plus concise Swagger or Postman documentation so the front-end team can plug in immediately.

If you have experience building high-volume REST APIs in Node.js, working with MongoDB transactions, and writing clean, well-documented code, I’d love to review a short outline of your approach and a realistic turnaround time.