Update a an application

Hello guys,
I have configured my docker-compose file to use Traefik v2.0 and a backend with python in a separate container with let's encrypt for SSL.

When there is an update in the backend code, I will run again the composer file with Traefik and the backend. I was wondering if Traefik was requesting a certificate each time I was running my docker-compose file or just using the previous certificate from the docker drivers?

Thank you.