solution.java

boolean updateValue(Event event) {
    long userInitiatedTimestamp = event.getUserInitiatedTimestamp();
    String userId = event.getUserId();
    User user = database.query(userId);
    long lastUserInitiatedTimestamp = user.getLastUserInitiatedTimestamp();
     
    // event arrives in correct order
    if(userInitiatedTimestamp > lastUserInitiatedTimestamp) {
        // register with latest timestamp
        user.setLastUserInitiatedTimestamp(userInitiatedTimestamp);
        user.setValue(event.getPayloadValue());
        return true;
    }
    else {
        // ignored
        return false;
    }
}