Workflows in CI
Many workflows in CI will build an image, and then subsequent steps will test that image in parallel. Docker registries are a commonly used storage mechanism for these intermediate build artifacts. One build step can push an image, and other distributed steps can pull. The challenge is that most registries require authentication to push and pull. A workflow can either bake credentials in and share them to build workers, or require forked builds to bring their own registry credentials. The first is insecure, the second creates friction for new contributors.
ttl.sh solves this by making an ephemeral and anonymous registry.