With the staggering dominance of public cloud providers, dev teams across the globe are increasingly focusing time and energy on optimizing their cloud development and deployment flows. The traditional deploy-and-test cycles against public clouds can become slow and tedious, where developers are often facing several minutes of idle times between deployments that need to be frequently triggered during testing & debugging. In this session, we provide a hands-on introduction to LocalStack (39k+ Github stars), a fully functional local AWS cloud stack. With LocalStack, applications can be developed entirely on your local machine, reducing dev&test cycles from minutes to seconds. The session covers interactive live coding to showcase common scenarios and use cases, different settings for local debugging of Lambdas and containerized apps (e.g., ECS/EKS), as well as some advanced new features that can radically improve productivity and team collaboration patterns. We will also glance over the large ecosystem of tools that LocalStack natively integrates with - from IaC frameworks like Terraform or Pulumi, to application frameworks like Serverless or Architect, to a whole suite of tools provided by AWS itself (CDK, SAM, Copilot, Chalice, etc). We'll wrap up the session with a deep dive into some of the Python internals of LocalStack, which reveals some interesting architectural patterns and hidden gems!