I built an open-source local AWS simulator for learning AWS — StackSim
A while ago I started a vibe-coding experiment with ChatGPT to see how far I could get emulating a few AWS services locally.
The original scope was pretty small: API Gateway, Lambda and DynamoDB.
It got slightly out of hand. 🙂
I’ve now made the project open source:
[**https://github.com/coolbeans47/stacksim
StackSim is intended as a **learning environment for AWS**, rather than something I’d recommend as a replacement for AWS in production.
One of the things I’ve deliberately tried to keep is that it’s **very simple to install and get running**. There’s no Docker stack, database server or complicated configuration required.
The main idea is that you can use normal AWS tooling against it locally. You can deploy ordinary **AWS CDK v2** applications, use the **AWS CLI**, and use the **AWS SDK for JavaScript v3** rather than learning a simulator-specific API.
It now has support across quite a few areas including:
CloudFormation/CDK
DynamoDB + Streams
Lambda
Step Functions
API Gateway
AppSync
S3
SQS / SNS
EventBridge + Scheduler
CloudWatch
IAM / STS
Cognito
SES
Parameter Store / Secrets Manager
a bounded local RDS profile
some Amplify Gen 2 support
There’s also a browser console so you can inspect what’s happening rather than treating everything as a black box.
I’ve added several example applications showing things such as event-driven architectures, Step Functions workflows, AppSync, Cognito/SAML, DynamoDB Streams, SNS fan-out, queues/DLQs and multi-stack CDK applications.
One thing I’ve deliberately tried to do is make unsupported functionality fail rather than silently pretend that AWS behaviour has been implemented.
This started purely as an experiment, but it became interesting enough that I thought it might actually be useful to people learning AWS, particularly anyone who wants to experiment without worrying about AWS accounts, cleanup, complicated local setup or unexpected costs.
I’d be interested in feedback — especially places where the simulated behaviour differs from AWS in ways that could teach somebody the wrong lesson.
Apache 2.0, completely open source.