Is it possible that "Server-side fan-out" can process with Firebase Cloud Functions?

Recently Cloud Functions has released on Firebase.

I'm developing social network service via Firebase and using "Fan-out" process for data consistency as explained on here.

Since "Client-side fan-out" is a bit inefficient for large data. Can we resolve this on Server-side with Cloud Functions?

If possible, can you guys give me a workaround to do this. Or if there is sample code with it please reference me.

For examples, if new data is inserted on posts node, how can we Fan-out this data on timeline node for each following user?

Thank you.

{
    "posts": {
        "-K-zOrtjiCGe7tgRk8DG": {
            "text": "I love emojis!",
            "uid": "user1"
        }
    },
    "timeline": {
        "user2": {
            "-K-zOrtjiCGe7tgRk8DG": {
                "text": "I love emojis!",
                "uid": "user1"
            }
        },
        "user3": {
            "-K-zOrtjiCGe7tgRk8DG": {
                "text": "I love emojis!",
                "uid": "user1"
            }
        }
    },
    "followers": {
        "user1": {
            "user2": true,
            "user3": true
        }
    }
}

via wonsuc