Overcast is alpha — behaviour and APIs may change between releases. Pin your version and read the changelog before upgrading.

overcast

Services

Service Reference

Index of every AWS service Overcast emulates, grouped by what you are building, with the coverage tiers and status tokens the service pages use.

One page per AWS service: a quick start, what works, and how it differs from AWS. Point any SDK or CLI at http://localhost:4566 and pick your service below.

export AWS_ENDPOINT_URL=http://localhost:4566
aws sqs create-queue --queue-name orders

Where to start

If you’re…Start with
Deploying a CDK or CloudFormation appCloudFormation, then Using AWS CDK
Building a serverless APILambda, API Gateway, DynamoDB
Wiring messaging and eventsSQS, SNS, EventBridge
Running containersECS, ECR, ELBv2
Storing objects or dataS3, DynamoDB, RDS

Services

Compute and containers — Lambda · ECS · ECR · EC2 / VPC · Auto Scaling · EKS

Storage and data — S3 · DynamoDB · DynamoDB Streams · RDS · ElastiCache · EFS · Kinesis · Firehose · MSK · Athena · Glue · OpenSearch · Backup · Transfer Family

Messaging and events — SQS · SNS · EventBridge · Scheduler · Pipes · Step Functions · SES

APIs and delivery — API Gateway · AppSync · CloudFront · ELBv2 · Route 53 · ACM

Identity and security — IAM · STS · Cognito · KMS · Secrets Manager · SSM · WAF v2 · Shield · Organizations

Observability — CloudWatch · CloudWatch Logs · CloudTrail

Provisioning and config — CloudFormation · AppConfig · AppConfigData · AppRegistry · Bedrock

Coverage tiers

Each service has an overall tier, and it decides the Status: token at the top of that service’s page. The full generated table, with operation counts and tiers, is on Reference index § Services.

TierMeaningPage status
ComprehensiveReal SDK clients use it end to end.✅ Supported
Core CRUDResources are created, stored and returned; common workflows work.⚠️ Partial
MinimalA targeted subset — enough for one or two workflows.⚠️ Partial
StubRegistered so discovery and IaC work; most operations return 501.⚠️ Partial

Each operation carries its own status token, and the service pages use the same five words for anything they qualify:

StatusMeaning
✅ SupportedWorks for normal SDK and CLI use.
⚠️ PartialWorks with documented caveats or missing edge cases.
🧊 InertAccepted and answered correctly, but nothing happens as a result.
🚧 WIPPresent, still moving.
❌ UnsupportedModelled but not implemented.

An unsupported operation answers with an AWS-shaped error rather than hanging or failing to connect, so an SDK raises something you can read:

HTTP 501 Not Implemented
x-emulator-unsupported: true

{
  "__type": "NotImplemented",
  "message": "This operation is not yet emulated. Check docs/services/ for the support matrix."
}

A running service also reports a runtime emulation tier — full, partial, inert or stub — on /_overcast/health, in overcast services and in the web console. That is a different axis, defined in Reference index § Runtime emulation tiers.