Floci
title: Floci type: tool created: 2026-05-19 last_updated: 2026-09-06 related: ["Playradar", "radar/techniques/LambdaUnitTesting", "radar/platforms/AWSVPCLattice"] sources: ["https://floci.io/", "https://github.com/floci-io/floci"] radar_quadrant: Tools radar_ring: Assess radar_position: inner
An open-source AWS emulator built with Quarkus Native that provides local AWS development and testing without cost, auth tokens, or restrictions. Wire-compatible with LocalStack on port 4566.
LocalStack began requiring a paid auth token in March 2026, removing unrestricted free local AWS emulation from the market. Floci was built to fill that gap under a permissive MIT licence with no sign-up, no telemetry, and no feature gating.
| Metric | Floci | LocalStack |
|---|---|---|
| Startup time | 24 ms | ~3,300 ms |
| Idle memory | 13 MiB | 143 MiB |
| Docker image size | ~90 MB | ~1 GB |
| Lambda throughput | 289 req/s | 120 req/s |
The 138x startup advantage is significant for CI/CD pipelines where emulator cold starts add to pipeline duration.
150+ AWS services as of 2026-09-06 (up from 68 on 2026-07-11 and 45 at first study), per Floci's own service-coverage documentation. Depth varies sharply by service: S3 has real versioning, lifecycle rules, presigned URLs, multipart upload, and object lock (replication is config-only with no actual object copy, and restore is stubbed); DynamoDB has real transactions, streams, GSI, and TTL (streams are best-effort rather than guaranteed-delivery, and LSI and PartiQL are undocumented); Lambda runs real Docker/k3s containers with layers, VPC config, container images, and event source mappings for SQS/Kinesis/DynamoDB, but has no provisioned concurrency and no destinations or DLQ support; IAM policy evaluation is off by default and must be explicitly enabled via an environment variable, and even then resource-based policies, NotPrincipal, and SCP simulation are unsupported. RDS, DocumentDB, ElastiCache, MemoryDB, and Neptune run real backing engines (PostgreSQL, MongoDB, Redis, Gremlin) but expose a narrow management API surface of only 7 to 14 operations each. The remaining roughly 140 services have published operation counts but no per-feature depth documentation found as of this study. SDK compatibility: 1,925 of 1,925 conformance tests passing.
Floci runs real service engines rather than mocking responses. Lambda functions execute in isolated Docker containers. RDS provides actual PostgreSQL or MySQL instances. Redis runs as a real container with IAM proxy authentication.
Floci does not emulate AWS VPC Lattice (see radar/platforms/AWSVPCLattice). Its networking coverage stops at Route53, Cloud Map, ELB v2, CloudFront, and API Gateway — VPC-level constructs (VPC Lattice, Transit Gateway, PrivateLink) are outside its current scope, which focuses on compute, data, and application services rather than the VPC networking layer. Confirmed by searching the floci-io/floci repository README and source for any "lattice" reference (none found, checked 2026-07-11).
Floci is wire-compatible: same port (4566), same credentials format. Switching requires changing no application code — only the Docker image reference. Services unavailable in LocalStack Community Edition (ElastiCache, RDS, API Gateway v2, Route53, Auto Scaling) are included in Floci.
Supports per-account isolation on a single instance, enabling multiple test environments or parallel CI runs on one machine.
floci-dash, a separate open-source project by ofsazib (26 stars, MIT licensed, actively maintained as of 2026-07-08), adds an AWS-Console-style web dashboard on top of Floci — browsing and managing S3 buckets, DynamoDB tables, Lambda functions, and other emulated services visually rather than through the AWS CLI or SDK. It runs alongside Floci (React + Hono + Docker) and does not change Floci's core emulation scope or ring placement.
Floci sits in the Assess ring of the Tools quadrant, at inner position. First studied via floci.io on 2026-05-19; no personal use of Floci specifically, though LocalStack was used previously. The LocalStack auth-token requirement (March 2026) makes Floci the natural free replacement. Inner position reflects a near-zero migration cost from LocalStack (wire-compatible, same port and credentials), MIT licence with no restrictions, and direct applicability to any existing AWS local development setup. The remaining gate before Trial is a completed substitution on an active project. Service coverage has grown from 45 to 68 to 150+ since first study, though VPC-level networking constructs such as VPC Lattice remain out of scope.
Compared against radar/tools/MiniStack on reward, risk, and API fidelity: Floci offers the higher reward (broader documented service count, 138x startup advantage, near-zero migration cost from a prior LocalStack setup) and carries the better-understood risk profile, since its gaps (opt-in IAM enforcement, missing Lambda provisioned concurrency) are documented by the vendor itself rather than left as unverified marketing claims. Its 1,925/1,925 SDK-conformance test result is also a concrete, checkable fidelity metric that MiniStack does not have an equivalent for. Floci is the recommended default AWS emulator between the two, with the caveat that any workload depending on IAM deny-by-default enforcement or Lambda provisioned concurrency should be smoke-tested first.
