kumo

Kumo is a single-binary AWS service emulator written in Go. It mocks 76 AWS services (S3, DynamoDB, Lambda, SQS, KMS, IAM) for local development and CI testing. No authentication required, AWS SDK v2 compatible, optional persistence. The pitch is LocalStack with less weight and no Docker dependency.

Setup is downloading a binary or running a container. Point your AWS SDK at the local endpoint and you get an emulator that does not ask for credentials. CI integration is straightforward because there is no auth dance and the binary boots fast. Set `KUMO_DATA_DIR` to keep state across restarts.

Solo developers: use it for CI tests and local dev without an AWS sandbox account. Small and mid-sized teams: a free way to keep AWS-dependent tests fast and predictable. Large teams: LocalStack Pro is still ahead on coverage breadth and edge case fidelity, so this is more of a niche pick than a wholesale replacement.

The catch: 76 services sounds like a lot, but coverage depth varies. Kumo is solid for the common cases (S3, DynamoDB, SQS) and weaker on niche APIs. Verify your specific use case before committing.