floci: LocalStack alternative with 24ms startup and 13MiB memory

An open-source emulator that runs AWS services locally without a cloud account or authentication tokens. It maintains existing AWS SDK, CLI, Terraform, and CDK setups, requiring only an endpoint change to http://localhost:4566. It is designed to address the feature limitations and discontinued security updates of the LocalStack Community Edition.

Core services such as Lambda, RDS, ECS, EC2, and EKS support actual Docker backend execution instead of shallow mocks. It covers a wide range of AWS services, including S3, DynamoDB, Cognito, and API Gateway v2, and is permanently free under the MIT license. The native binary is approximately 40MB in size and runs on Linux, macOS, and Windows without Docker.

Performance shows a clear difference from existing methods. Startup time is approximately 24ms, and idle memory is approximately 13MiB, making it suitable for CI pipelines. The Docker image size is approximately 90MB, which is one-tenth the size of the LocalStack Community Edition. Storage profiles such as in-memory, persistent, hybrid, and WAL can be selected according to the situation.

It includes a browser-based web console for real-time monitoring of local resources. LocalStack users can migrate immediately by simply replacing the image. It is suitable for developers who want to remove cloud dependencies, from setting up local development environments to CI testing.