Push, Cache, Repeat: Amazon ECR as a remote Docker cache for GitHub Actions

Docker layer caching can substantially accelerate GitHub Actions image builds by reusing unchanged layers, but GitHub-hosted runners are ephemeral and cannot reliably retain local caches between jobs. The described approach stores BuildKit cache artifacts separately in AWS Elastic Container Registry, beginning with a standard workflow that authenticates to ECR and builds and pushes an image. Remote caching requires Docker Buildx, configured through the setup-buildx GitHub Action and a builder instance, with cache-from pointing to an existing ECR cache image and cache-to publishing updated cache layers using registry-compatible options. The workflow supports private ECR repositories, while public ECR requires different cache reference URLs, and ECR IAM permissions may need to include authorization, image retrieval, and layer-upload operations to avoid 403 errors.

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