Upload Files to S3 with FastAPI, Locally with Ministack

In this video, you’ll learn how to upload files to Amazon S3 from a FastAPI application without ever touching the real AWS cloud. We use Ministack — a free, open-source LocalStack replacement that emulates AWS services on your machine — so you can develop and test your file upload workflow entirely locally.

What You’ll Learn

By the end of this video, you will be able to:

• Upload files using FastAPI
• Run a local S3-compatible server with Ministack
• Create buckets and upload objects using boto3
• Build a file upload endpoint in FastAPI
• Point the AWS SDK at a custom endpoint URL for local development

What is Ministack?

Ministack is a free, open-source AWS emulator — a lightweight LocalStack alternative. It emulates many AWS services (including S3) right on your machine, and it is drop-in compatible with boto3, the AWS CLI, Terraform, CDK, Pulumi, and any other AWS SDK or tool. This means the code you write against Ministack locally works unchanged when pointed at real AWS.

Prerequisites

• Python 3.10+ installed
• Docker (for running Ministack)
• Basic familiarity with FastAPI

Quick Start

Start Ministack with Docker:

docker run -p 4566:4566 ministackorg/ministack

Because Ministack speaks the same protocol as real S3, switching to production is as simple as removing the endpoint_url and adding your AWS credentials.

Watch the full video above for the complete step-by-step walkthrough.