Some events are not part of the game play data and therefore do not belong in a session. Typically these will be server events that are triggered due to something other than the player playing the game. Therefore it would be inconvenient if sending an event would make it seem like the player was playing at this point in time. If you want to send an event as such then you can omit the session ID and the eventTimestamp, we will then stitch the event back into the end of the last session the played for that player. This can be useful for attribution data or enriching old users with newly acquired data for example.