Thursday, 12 November 2026, story 2 of 7
AWS releases an official local emulator for testing against its APIs
The Rust-based AWS Emulator needs no AWS account and carries no service fee, but macOS and Windows users must run it in Docker.
What happened
AWS has published AWS Emulator, a local program that serves an AWS API endpoint so code can be tested without calling AWS. Its README says no AWS account is needed and there is no additional service fee. Simon Willison, who flagged it on 11 November, says it is written in Rust by a swarm of agents, with 29,684 commits in the project's first three weeks.
Linux users install an RPM or Debian package. On macOS and Windows it runs in a container. Rust tests can embed it, one instance per test. The README says it is not for production workloads or security testing.
What it means
The practical gain is tests and CI that run without an AWS account or a bill for test resources. The cost shifts from cloud spend to local setup. Embedded mode compiles every service crate into the test binary, and the README says to budget a first build and target/ directory comparable to building from source, which needs at least 100 GB of free disk. Rust teams will want a shared target directory and CI caching.
Usefulness depends on fidelity, not commit counts. The README points to per-release fidelity scores and a public list of known gaps, and that is where to check first. Telemetry is on by default and can be switched off. Willison's hope for a single binary on macOS and Windows is unmet for now.
What to do: Before moving a test suite onto it, read the fidelity scores for the services you use and decide whether to switch telemetry off in CI.
Sources
- aws-emulator, Simon Willison
- AWS emulator, github.com
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