Floci is a local AWS service emulator — a drop-in replacement for LocalStack’s community edition that requires no auth token, has no usage limits, and is MIT-licensed.
The name comes from cirrocumulus floccus, a small, fluffy cloud formation. That’s the design goal: minimal, lightweight, and always free.
GitHub: github.com/hectorvent/floci
Native Floci vs LocalStack
| Metric | Native Floci | LocalStack | Advantage |
|---|---|---|---|
| Startup Time | ~24 ms | ~3,300 ms | 138× faster |
| Idle Memory | ~13 MiB | ~143 MiB | 91% less |
| Lambda Latency | 2 ms avg | 10 ms avg | 5× faster |
| Lambda Throughput | 289 req/s | 120 req/s | 2.4× faster |
| Docker Image Size | ~90 MB | ~1.0 GB | 11× smaller |
| Price | Free Forever | Auth Token Req. | $0 / No Auth |
Supported AWS Services
SSM · SQS · SNS · S3 · DynamoDB · DynamoDB Streams · Lambda · API Gateway REST · API Gateway v2 · IAM · STS · Cognito · KMS · Kinesis · Secrets Manager · CloudFormation · Step Functions · ElastiCache · RDS · EventBridge · CloudWatch Logs · CloudWatch Metrics
Lambda functions run inside real Docker containers (Node.js, Python, Java, Go, Ruby) with a warm pool for sub-millisecond reuse. ElastiCache and RDS spin up actual Redis and database containers on demand. All 408 AWS SDK v2 compatibility checks pass.
Stack
- Java 25 + Quarkus 3.x — reactive, lightweight runtime
- GraalVM Mandrel — compiles to a native binary with no JVM required
- Vert.x — embedded HTTP server for the Lambda Runtime API
- docker-java — container lifecycle management
- MIT License
Quick Start
docker run --rm -p 4566:4566 hectorvent/floci:latest
Then point any AWS SDK or CLI at http://localhost:4566 with any dummy credentials.
Read the full deep-dive on the blog.