If your custom app needs to send orders or invoices to an ERP, don't call the ERP API from inside your request handler. Write each change to an outbox table in the same Postgres transaction as the business data. Then let a separate Node.js worker push those rows to the ERP, with retries, backoff and a dead-letter queue. This is the part of ERP development that decides whether you can sync records between a custom app and your ERP without losing any or posting them twice.

You may know the symptoms already. The ERP had a slow afternoon and some orders never arrived. Or the warehouse shipped one order and finance has two invoices for it. Nobody can say which records made it across without checking both systems by hand.

How do you sync records between a custom app and your ERP without losing any?

You make the database the single source of truth for what still needs to be sent. The outbox row and the order row commit together or not at all.…