Fakecloud is a free local AWS emulator with 105 services and no account, aimed at LocalStack Community users now pushed to a paid plan

Local test suites that used to run against LocalStack Community now need a personal account and an auth token, and several service families they used to cover for free were moved to paid tiers. A developer using the handle faiscadev posted Fakecloud to Hacker News on 26 September, a free open-source AWS cloud emulator written in Rust that ships as a single binary and needs no account, token or paid plan to run. The Show HN reached 105 points and the underlying GitHub repository crossed 630 stars in its first two days on the front page.

Fakecloud says it covers 105 AWS services and 7,508 operations, and that it passes 248,557 of 248,557 test variants generated from Amazon's own Smithy service models, which its authors call true 100% conformance across all 3,932 implemented API operations. The services list includes S3, SQS, SNS, DynamoDB, Lambda, EC2, Cognito, Step Functions, API Gateway v1 and v2, and four Bedrock APIs (Bedrock, Bedrock Runtime, Bedrock Agent and Bedrock Agent Runtime), so teams that build with AWS-hosted models can exercise agent calls locally as well. Cross-service flows like S3 event notifications, SNS fanout, EventBridge targets, DynamoDB Streams, CloudWatch Logs subscriptions and API Gateway to Lambda are wired up rather than stubbed. The licence is AGPL-3.0.

The comparison Fakecloud draws with LocalStack

The project's home page runs a table against LocalStack Community, and every claim in it is Fakecloud's own. Fakecloud says LocalStack Community now requires a personal account and auth token to start, and that several service families that used to be free in the Community tier are only available on paid plans, including Cognito User Pools, SES v2, RDS, ElastiCache, MemoryDB, EKS and API Gateway v2. Fakecloud lists all of these among its 105 services and prices them at zero. It also states its own binary is 19 MB and starts in 300 ms with 10 MiB of idle memory, against a 1 GB Docker image, 3 second startup and 150 MiB idle for LocalStack Community. LocalStack has not responded to these specific claims.

What the SDKs actually do

Application code keeps using the normal AWS SDK against localhost:4566. Fakecloud publishes first-party test SDKs on npm, PyPI, Maven, crates.io, Packagist and pkg.go.dev, in TypeScript, Python, Go, PHP, Java and Rust. Those clients wrap a separate /_fakecloud/* set of introspection endpoints, so tests can reset state between runs, read the SES emails or SNS messages the app just sent, replay Lambda invocations, pull Cognito confirmation codes, or force asynchronous processors to run on demand. The project says this pattern is meant to keep test code short: the app under test uses real AWS clients, and only the assertion step reaches for a fakecloud-specific helper.

Fakecloud is an emulator, not real AWS, and corners will differ from the real service in edge cases. The AGPL-3.0 licence also has stronger copyleft terms than LocalStack's proprietary base for teams that plan to distribute anything built on top of it, so a legal review belongs before this becomes part of a CI pipeline.

For a team building on AWS, the practical effect of a working local emulator is that fast feedback moves back to the developer's laptop. When a suite that used to hit a shared staging account can run against localhost in under a second per test, agents and humans both stop waiting on network latency and rate limits, and a serious free alternative to LocalStack Community is worth adding to the shortlist.

Source

Primary source: fakecloud.dev. Repository: faiscadev/fakecloud on GitHub. Show HN discussion: Fakecloud: Local AWS cloud emulator for integration tests.