MildStack: Free Open Source LocalStack Alternative

MildStack emulates core AWS services locally. Learn what's supported and how to use S3, DynamoDB, and SQS in your development workflow.

Supported Services

MildStack provides local emulations of the most commonly used AWS services. Each service is fully compatible with the official AWS SDKs and CLI — just point your application to the local endpoint.

Amazon S3

Object storage — buckets, objects, multipart uploads, versioning, and more.

Amazon DynamoDB

NoSQL database — tables, items, queries, scans, and batch operations.

Amazon SQS

Message queues — standard and FIFO queues, dead-letter queues, and message operations.

Connecting to Services

All services share the same endpoint. Just point your AWS SDK to MildStack:

Setting	Value
Endpoint URL	`http://localhost:4566` (or your custom port)
Region	`us-east-1` (default)
Access Key	Any value (e.g., `test`)
Secret Key	Any value (e.g., `test`)

import { S3Client } from "@aws-sdk/client-s3";

const client = new S3Client({
  region: "us-east-1",
  endpoint: "http://localhost:4566",
  credentials: {
    accessKeyId: "test",
    secretAccessKey: "test",
  },
  forcePathStyle: true,
});

MildStack does not validate credentials. Use any dummy values — they exist only to satisfy SDK requirements.

Service Availability

All services start automatically when you launch a MildStack instance. There's no need to enable or configure individual services — everything is ready to use immediately.

# Start MildStack — all services are available
mildstack start

Benefits of Local Development

Benefit	Description
No internet required	Build and test offline, on a plane, or anywhere
Instant feedback	No deployment delays — changes are reflected immediately
Zero cost	No AWS charges during development
Full control	Create complex test scenarios deterministically
Data privacy	Sensitive development data stays on your machine

Planned Services

We're actively working on expanding our service coverage:

Service	Status
Amazon SNS	🔜 In development
AWS Lambda	📅 Planned
Amazon EventBridge	📅 Planned

MildStack aims for high compatibility with the AWS APIs. We focus on the operations that matter most for local development and testing. Each service page lists the specific operations that are supported.

If you encounter a missing operation or unexpected behavior, please open an issue on GitHub.

Services