We have exactly the same problem at work. One possible way to solve it is by ensuring that the receiving system treats the request as idempotent. One could also

We have exactly the same problem at work. One possible way to solve it is by ensuring that the receiving system treats the request as idempotent. One could also poll first at the receiver whether the transaction exists, and then send it if it doesn't. But both measures require that there is a way to uniquely identify a request. Also, idempotency can be annoying to implement correctly. Thus, implementors might try to wiggle their way out of it, technically or politically.