What is openliberty transaction manager backend routing?

Java EE application server OpenLiberty documentation has a configurable property "backendURL" for transaction managers.

When backend routing is active, the URL is used by peer servers to contact this server. https://openliberty.io/docs/latest/reference/config/transaction.html

What is "backend routing" used for in this context?

I have two guesses:

1. It could be for transaction recovery when a peer needs to figure out if a server is alive or not.
2. It could be for rerouting when a transaction coordination request has been routed to wrong peer and the request needs to be rerouted to the correct server where the coordinating transaction manager can be found.

I have tried to Google it, but did not find anything except the link to the documentation which is in the question part. Reading the documentation did not explain what the backend routing is used for.

Your second guess is correct. The backendURL is the address at which a server can be contacted by its peers.