aws-serverless

AWS Serverless Plugin

Overview

Build and deploy serverless applications with AWS Lambda, SAM, API Gateway, and the complete AWS serverless ecosystem. This skill provides access to comprehensive serverless development tools through the AWS Serverless MCP Server, enabling you to build production-ready serverless applications with best practices built-in.

Use SAM CLI for project initialization and deployment, Lambda Web Adapter for web applications, or Event Source Mappings for event-driven architectures. The platform handles infrastructure provisioning, scaling, and monitoring automatically.

Key capabilities:

• SAM CLI Integration: Initialize, build, deploy, and test serverless applications
• Web Application Deployment: Deploy full-stack applications with Lambda Web Adapter
• Event Source Mappings: Configure Lambda triggers for DynamoDB, Kinesis, SQS, Kafka
• Schema Management: Type-safe EventBridge integration with schema registry
• Observability: CloudWatch logs, metrics, and X-Ray tracing
• Performance Optimization: Right-sizing, cost optimization, and troubleshooting

Workflow Guidance

Refer to these supporting files for detailed guidance on specific workflows:

File	When to Use
getting-started.md	Decision tree: what are you building? Routes to the right template, runtime, and guide
sam-project-setup.md	SAM project initialization, template selection, development workflow, and testing
cdk-project-setup.md	CDK as an alternative to SAM: constructs, patterns, testing, and deployment
web-app-deployment.md	Full-stack deployment patterns with Lambda Web Adapter, authentication, and response streaming
event-sources.md	Lambda event sources: S3, SNS, DynamoDB, Kinesis, SQS, Kafka, MQ, and DocumentDB
event-driven-architecture.md	EventBridge rules, event design, choreography vs orchestration, Pipes, schema registry
orchestration-and-workflows.md	Multi-step workflows with Lambda Durable Functions or Step Functions
optimization.md	Performance tuning, cost optimization, Lambda SnapStart, Managed Instances, and Powertools
observability.md	Structured logging, distributed tracing, custom metrics, alarms, dashboards, and Logs Insights
troubleshooting.md	Symptom-based diagnosis and resolution for common issues

Best Practices

Project Setup

• Do: Use sam_init or cdk init with an appropriate template for your use case
• Do: Set global defaults for timeout, memory, runtime, and tracing (Globals in SAM, construct props in CDK)
• Do: Use AWS Lambda Powertools for structured logging, tracing, metrics (EMF), idempotency, and batch processing — available for Python, TypeScript, Java, and .NET
• Don't: Copy-paste templates from the internet without understanding the resource configuration
• Don't: Use the same memory and timeout values for all functions regardless of workload

Security

• Do: Follow least-privilege IAM policies scoped to specific resources and actions
• Do: Use secure_esm_* tools to generate correct IAM policies for event source mappings
• Do: Store secrets in AWS Secrets Manager or SSM Parameter Store, never in environment variables
• Do: Use VPC endpoints instead of NAT Gateways for AWS service access when possible
• Do: Enable Amazon GuardDuty Lambda Protection to monitor function network activity for threats (cryptocurrency mining, data exfiltration, C2 callbacks)
• Don't: Use wildcard (*) resource ARNs or actions in IAM policies
• Don't: Hardcode credentials or secrets in application code or templates
• Don't: Store user data or sensitive information in module-level variables — execution environments can be reused across different callers

Idempotency

• Do: Write idempotent function code — Lambda delivers events at least once, so duplicate invocations must be safe
• Do: Use the AWS Lambda Powertools Idempotency utility (backed by DynamoDB) for critical operations
• Do: Validate and deduplicate events at the start of the handler before performing side effects
• Don't: Assume an event will only ever be processed once

For topic-specific best practices, see the dedicated guide files in the Workflow Guidance table above.

Lambda Limits Quick Reference

Limits that developers commonly hit:

Resource	Limit
Function timeout	900 seconds (15 minutes)
Memory	128 MB – 10,240 MB
1 vCPU equivalent	1,769 MB memory
Synchronous payload (request + response)	6 MB each
Async invocation payload	1 MB
Streamed response	200 MB
Deployment package (.zip, uncompressed)	250 MB
Deployment package (.zip upload, compressed)	50 MB
Container image	10 GB
Layers per function	5
Environment variables (aggregate)	4 KB
/tmp ephemeral storage	512 MB – 10,240 MB
Account concurrent executions (default)	1,000 (requestable increase)
Burst scaling rate	1,000 new executions per 10 seconds

Check Service Quotas for your account limits: aws lambda get-account-settings

Troubleshooting Quick Reference

Error	Cause	Solution
Build Failed	Missing dependencies	Run sam_build with use_container: true
Stack is in ROLLBACK_COMPLETE	Previous deploy failed	Delete stack with aws cloudformation delete-stack, redeploy
IteratorAge increasing	Stream consumer falling behind	Increase ParallelizationFactor and BatchSize. Use esm_optimize
EventBridge events silently dropped	No DLQ, retries exhausted	Add RetryPolicy + DeadLetterConfig to rule target
Step Functions failing silently	No retry on Task state	Add Retry with Lambda.ServiceException, Lambda.AWSLambdaException
Durable Function not resuming	Missing IAM permissions	Add lambda:CheckpointDurableExecution and lambda:GetDurableExecutionState

For detailed troubleshooting, see troubleshooting.md.

Configuration

Authentication Setup

This skill requires AWS credentials configured on the host machine:

1. Install AWS CLI: Follow the AWS CLI installation guide
2. Configure credentials: Run aws configure or set up named profiles in ~/.aws/credentials
3. Set environment variables (if not using the default profile):
   • AWS_PROFILE - Named profile to use
   • AWS_REGION - Target AWS region
4. Verify access: Run aws sts get-caller-identity to confirm credentials are valid

SAM CLI Setup

1. Install SAM CLI: Follow the SAM CLI installation guide
2. Install Docker Desktop: Required for sam_local_invoke and container-based builds
3. Verify: Run sam --version and docker --version

MCP Server Configuration

The MCP server is configured in .mcp.json with the following flags:

• --allow-write: Enables write operations (project creation, deployments)
• --allow-sensitive-data-access: Enables access to Lambda logs and API Gateway logs

SAM Template Validation Hook

This plugin includes a PostToolUse hook that runs sam validate automatically after any edit to template.yaml or template.yml. If validation fails, the error is returned as a system message so you can fix it immediately. The hook requires SAM CLI to be installed and silently skips if it is not available. Users can disable it via /hooks.

Version policy: .mcp.json uses awslabs.aws-serverless-mcp-server@latest. This is intentional — the package is pre-1.0 (currently 0.1.x) and under active development, so pinning would miss bug fixes and new tool capabilities. If you need a stable, reproducible setup, pin to a specific version:

"args": ["awslabs.aws-serverless-mcp-server@0.1.17", "--allow-write", "--allow-sensitive-data-access"]

Check for new versions with uvx pip index versions awslabs.aws-serverless-mcp-server.