Photos of Landmarks are taken and posted to Discord through a process that takes a snapshot of the stream and automatically posts that as an image to Discord. This action is triggered by viewers redeeming a Twitch Channel Points reward.

The moment of posting the photo is when a Landmark is officially marked as visited or a Gate officially marked as locked. If both players arrive at their respective Landmark at the exact same time and upload their photos on the exact same moment on their Discord, then the photo with the lowest Discord Message ID wins.

What is a Discord Message ID?

Each message on Discord gets its own ID. This is a unique, very long number. This number is always increasing with every message sent by everybody using Discord in the world. With each new message sent, the ID gets increased by 1. Such an ID might look like this:

1166446027700703252 
1166446027700703184

As you can see from the numbers above, the second ID is lower than the first ID. Therefore the second message is posted earlier.