AWS Lambda Serverless Development

Design, build, deploy, and debug serverless applications with AWS serverless services. This skill provides access to serverless development guidance through the AWS Serverless MCP Server, helping 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. AWS 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
• Lambda durable functions: Resilient multi-step applications with checkpointing — see the durable-functions skill for guidance
• 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

When to Load Reference Files

Load the appropriate reference file based on what the user is working on:

• Getting started, what to build, project type decision, or working with existing projects -> see references/getting-started.md
• SAM, CDK, deployment, IaC templates, CDK constructs, or CI/CD pipelines -> see the aws-serverless-deployment skill (separate skill in this plugin)
• Web app deployment, Lambda Web Adapter, API endpoints, CORS, authentication, custom domains, or sam local start-api -> see references/web-app-deployment.md
• Event sources, DynamoDB Streams, Kinesis, SQS, Kafka, S3 notifications, or SNS -> see references/event-sources.md
• EventBridge, event bus, event patterns, event design, Pipes, or schema registry -> see references/event-driven-architecture.md
• Durable functions, checkpointing, replay model, saga pattern, or long-running Lambda workflows -> see the durable-functions skill (separate skill in this plugin with full SDK reference, testing, and deployment guides)
• Orchestration, workflows, or Durable Functions vs Step Functions -> see references/orchestration-and-workflows.md
• Step Functions, ASL, state machines, JSONata, Distributed Map, or SDK integrations -> see references/step-functions.md
• Step Functions testing, TestState API, mocking service integrations, or state machine unit tests -> see references/step-functions-testing.md
• Observability, logging, tracing, metrics, alarms, or dashboards -> see references/observability.md
• Optimization, cold starts, memory tuning, cost, or streaming -> see references/optimization.md
• Powertools, idempotency, feature flags, parameters, parser, batch processing, or data masking -> see references/powertools.md
• Troubleshooting, errors, debugging, or deployment failures -> see references/troubleshooting.md

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 reference table above.

Lambda Limits Quick Reference

Limits that developers commonly hit:

/tmp

Check Service Quotas for your account limits:

aws lambda get-account-settings

Troubleshooting Quick Reference

Build Failed

sam_build

use_container: true

Stack is in ROLLBACK_COMPLETE

aws cloudformation delete-stack

IteratorAge

ParallelizationFactor

BatchSize

esm_optimize

RetryPolicy

DeadLetterConfig

Retry

Lambda.ServiceException

Lambda.AWSLambdaException

lambda:CheckpointDurableExecution

lambda:GetDurableExecutionState

For detailed troubleshooting, see references/troubleshooting.md.

Configuration

AWS CLI Setup

This skill requires that AWS credentials are configured on the host machine:

Verify access: Run

aws sts get-caller-identity

SAM CLI Setup

1. Install SAM CLI: Follow the SAM CLI installation guide
2. Verify: Run

   sam --version

Container Runtime Setup

1. Install a Docker compatible container runtime: Required for

   sam_local_invoke

   and container-based builds
2. Verify: Use an appropriate command such as

   docker --version

   or

   finch --version

MCP Server Configuration

Write access is enabled by default. The plugin ships with

--allow-write

.mcp.json

Access to sensitive data (like Lambda and API Gateway logs) is not enabled by default. To grant it, add

--allow-sensitive-data-access

.mcp.json

SAM Template Validation Hook

This plugin includes a

PostToolUse

sam validate

template.yaml

template.yml

jq

/hooks

Verify: Run

jq --version

Language selection

Default: TypeScript

Override syntax:

• "use Python" → Generate Python code
• "use JavaScript" → Generate JavaScript code

When not specified, ALWAYS use TypeScript

IaC framework selection

Default: CDK

Override syntax:

• "use CloudFormation" → Generate YAML templates
• "use SAM" → Generate YAML templates

When not specified, ALWAYS use CDK

Serverless MCP Server Unavailable

• Inform user: "AWS Serverless MCP not responding"
• Ask: "Proceed without MCP support?"
• DO NOT continue without user confirmation

Resources

• AWS SAM Documentation
• AWS Lambda Documentation
• AWS Lambda Powertools
• AWS CDK Documentation
• AWS Serverless MCP Server