When an already existing poster exists in the database, we return the image that's already been generated. This makes sure requests are fast and that we use as little storage and compute as possible.

On April 12, 2020, we added the ability to let users choose a skin tone for the generated poster. Before this, all generated posters had a light skin tone—the default skin tone on the NHS graphic that we base all our posters from.

This means that most of the generated posters use the light skin tone. In order to save storage space, we default to this skin tone so users that don't select a different skin tone hit the pre-existing database of over half a million posters