“"24ms startup is the real story. You can treat it as disposable: fresh instance per test run." — 4riel (https://news.ycombinator.com/item?id=47471801)”
You know that feeling when your integration tests hit real AWS and you're paying per API call just for CI runs — or watching a test fail because someone else's test left a dirty S3 bucket in the shared dev account? LocalStack Community Edition was the standard fix: run a local fake AWS on port 4566, tests finish in milliseconds, CI stays deterministic. Then LocalStack archived its Community Edition on March 23, 2026 and added a mandatory auth token requirement, leaving every team that relied on the free tier with no maintained replacement and a pile of suddenly-broken CI pipelines.
Floci runs as a single Docker container on port 4566 — the same port LocalStack used. When your code makes an AWS SDK call to SQS, DynamoDB, or S3, the request hits Floci's in-process handler instead of the real AWS. For stateful services that need genuine engine behavior — Lambda, RDS, EKS — Floci spins up real Docker child containers: your Lambda runs in an actual AWS Lambda runtime, your RDS call connects to a real PostgreSQL instance. Quarkus Native (GraalVM AOT compilation) compresses the JVM startup from seconds into 24ms. You set any dummy AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY, point the SDK endpoint at localhost:4566, and existing init scripts from /etc/localstack/init/ run unchanged.
If you're a backend engineer running AWS integration tests in CI — especially S3, SQS, DynamoDB, Lambda, or RDS — and your team was using LocalStack Community Edition before March 2026, Floci is the lowest-friction replacement. It's also worth evaluating if you're setting up a new project and want deterministic AWS testing without cloud costs. Not useful yet if you need Windows compatibility (open issue #739 as of 2026-05-12), or if you depend on services outside Floci's 46-service catalog.
Worth testing immediately if your team migrated off LocalStack Community Edition in March 2026 — the migration is wire-compatible and takes less than one sprint. The v1.0 to v1.5.14 pace in 8 weeks shows strong shipping cadence, but two open issues should stop you before full production CI adoption: issue #695 (LocalStack env-var compatibility incomplete) and the Docker socket mount as root (a container escape risk in shared runners). Run your full test suite in a spike before committing.
Deep-dive insight, Easy and Pro modes, plus action playbooks — the full breakdown is one tap away.