Docker Hub (the default registry for hosting Docker images) has scheduled downtime for Saturday, August 25: https://success.docker.com/article/planned-downtime-on-hub-cloud-store
Aptible Enclave will be failing over to a different registry during this scheduled maintenance, so all Enclave-internal images required for app and database operations will continue to be accessible throughout the downtime.
That being said, as an Aptible Enclave customer, you might be deploying Docker images that depend on the Docker Hub directly or indirectly:
If you're using (git push-based) Dockerfile Deploy, your base image (the one referenced in the FROM instruction of your Dockerfile) may be hosted on Docker Hub. Such apps will not be deployable during the Docker Hub downtime unless you mirror the base image to an alternate registry ahead of time. All Aptible base images are mirrored on Quay.io, so if you are using one of those, you can update your Dockerfile to reference the Quay-mirrored version (just add "quay.io/" to the beginning of the image). Check here for the listed of mirrored images: https://quay.io/organization/aptible
If you're using Direct Docker Image Deploy and your base image is hosted on Docker Hub, you'll need to mirror it on an alternate registry before the downtime in order to deploy.
As always, if you have any questions, please don't hesitate to reach out by emailing firstname.lastname@example.org