If you’ve been following AWS local development tooling, you probably noticed that LocalStack Community Edition started requiring auth tokens and moved features behind paid tiers in early 2026. That left a real gap for developers who just want to run AWS services locally. No account, no quotas, no strings attached.
That’s exactly why I built Floci.
What is Floci?
Floci is a free, open-source local AWS emulator written in Java with Quarkus and compiled to a native binary via GraalVM. It runs on port 4566, the same port as LocalStack, so switching requires changing just one environment variable.
The name comes from cirrocumulus floccus, a lightweight, popcorn-like cloud formation. The ethos: minimal footprint, fast startup, zero overhead.
Why it’s different
| Metric | Native Floci | LocalStack |
|---|---|---|
| Startup time | ~24 ms | ~3,300 ms |
| Idle memory | ~13 MiB | ~143 MiB |
| Image size | ~90 MB | ~2 GB |
| Auth required | Never | Yes |
| Price | Free forever | Paid tiers |
Beyond the numbers, Floci runs real Docker-backed services for Lambda, RDS (PostgreSQL/MySQL), ElastiCache, MSK, OpenSearch, ECS, and EKS (not shallow mocks). It also ships with 1,850+ automated SDK compatibility tests covering Java v2, JavaScript v3, boto3, AWS CLI v2, Go v2, and Rust.
Quick start
docker run -p 4566:4566 floci/floci:latest
export AWS_ENDPOINT_URL="http://localhost:4566"
aws s3 mb s3://my-bucket
Testcontainers and Spring Boot auto-configuration are available on Maven Central for seamless integration in your test suites.
Supported services
Floci covers 40+ AWS services including S3, SQS, SNS, DynamoDB (with Streams), Lambda, API Gateway, Cognito, KMS, Secrets Manager, IAM, STS, Step Functions, CloudFormation, EventBridge, CloudWatch, and Kinesis.
For the full write-up including architecture details, benchmark methodology, and the roadmap read the original post on dev.to:
Meet Floci: a fast, free, no-strings AWS emulator (no auth token, no quotas)