The requirements describe a Git-driven workflow where each new branch automatically gets its own deployment with minimal setup and management. AWS Amplify is designed for exactly this use case for web (and supporting mobile backends): it integrates directly with Git providers and offers continuous deployment . Amplify’s feature branch deployments automatically create a separate deployment (and typically a distinct preview URL) for each connected branch, enabling developers to test and review changes per branch without manually provisioning environments.

With Amplify, the developer connects the repository once, selects the branches to deploy, and Amplify automatically builds and deploys the application whenever code changes are pushed. When a new branch is added, Amplify can be configured to deploy it as a separate environment, providing isolated testing, previewing, and validation. This dramatically reduces operational overhead because Amplify manages build settings, hosting, SSL, and branch-based environments without needing custom CI/CD wiring.

Option A (ECR + ECS + GitHub Actions) can support branch deployments, but it requires substantial operational work: container build pipelines, task/service management, networking, scaling, and environment isolation per branch. Option B (Elastic Beanstalk) can manage deployments, but branch-based automatic deployments are not as native; creating separate environments and managing application versions typically requires more manual steps or additional automation. Option C (Lambda aliases) is not a general-purpose web/mobile deployment approach and does not naturally map “new Git branch” to an isolated deployment environment without significant custom tooling.

Therefore, D is the best fit with the least operational overhead: use AWS Amplify with feature branch deployments to automatically create and manage separate deployments for Git branches.