Hey @Vivat
We have an example for deleting a node here. Essentially, you just marshal the uid of the node to be deleted and send it using DeleteJson.
This message indicates that the related node or indexes were modified by some other transaction. This is a temporary error and we recommend that you retry the transaction when you get this error. You could also set IgnoreIndexConflict to be true while adding mutations which would reduce the probability of aborts.