Technical questions
Can it be used after the event is over?
The short answer
Yes. Much of Matcha's value comes after the event, once the photos are ready to share.
At an event with personal galleries, sharing afterwards is usually the main moment. The guests are already home, and that is when they get an easy way to see their photos.
Agree in advance on when you plan to open the galleries, based on how long the photographer will need to finish and upload the photos.