How can I use a transaction while performing a multi-location update in Firebase?

Question

In my Firebase database, I need two write to two locations at once. I have rules for both locations that ensure that a user can\'t write there without simultaneously writing

Answer 1

It is now possible to combine multi-path updates with transactions with the introduction of ServerValue.increment()

Example:

Map postLikeUpdate = new HashMap<>();
postLikeUpdate.put("postLikedBy/" + postId + "/" + userId, true);
postLikeUpdate.put("likesCount/" + postId, ServerValue.increment(1));
FirebaseDatabase.getInstance().getReference().updateChildren(postLikeUpdate);

Link to release notes