aws-lambda-durable-functions
Builds resilient, long-running, multi-step applications with AWS Lambda durable functions with automatic state persistence, retry logic, and orchestration for long-running executions. Covers the critical replay model, step operations, wait/callback patterns, error handling with saga pattern, testing with LocalDurableTestRunner. Triggers on phrases like lambda durable functions, durable execution, workflow orchestration, state machines, retry/checkpoint patterns, long-running stateful Lambda functions, saga pattern, human-in-the-loop callbacks, reliable serverless applications, context.step, context.wait, context.invoke, context.runInChildContext, withDurableExecution, DurableContext, UnrecoverableInvocationError, durable-execution-sdk, qualified ARN invocation, and durable handler replay.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/aws/agent-toolkit-for-aws --skill aws-lambda-durable-functions- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads aws-lambda-durable-functions automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
Security audits
Independent scans of the skill's instructions and bundled files.
SKILL.md
The instructions your agent reads when the skill is triggered.
AWS Lambda durable functions
Build resilient multi-step applications and AI workflows that can execute for up to 1 year while maintaining reliable progress despite interruptions.
Works best with the AWS MCP server but is not required. All AWS interactions in this skill use standard AWS CLI commands that work in any environment with configured AWS credentials.
Critical Rules
Read these before writing any code. Each one is a constraint that will silently break a function if violated.
- Durable execution must be enabled at function creation time — it cannot be retrofitted. A new Lambda function must be created with durable execution turned on. Migrate the logic into the new function; do not attempt to install the SDK and wrap the handler of the existing function and expect it to work.
- Durable functions must be invoked with a qualified ARN — a specific version, an alias, or the literal
$LATESTsuffix. An unqualified function name will fail. See the Invocation Requirements section below for examples. - Durable operations cannot be nested. You cannot call
context.step(),context.wait(), orcontext.invoke()from inside another step's callback. Usecontext.runInChildContext()to group operations instead. - All non-deterministic code must run inside steps.
Date.now(),Math.random(), UUID generation, API calls, and database queries outside a step will produce different values on replay and corrupt execution state. - Closure mutations are lost on replay - return values from steps
- Side effects outside steps repeat - use
context.logger(replay-aware)
When to Load Reference Files
Load the appropriate reference file based on what the user is working on:
- Getting started, basic setup, example, ESLint, or Jest setup -> see getting-started.md
- Understanding replay model, determinism, or non-deterministic errors -> see replay-model-rules.md
- Creating steps, atomic operations, or retry logic -> see step-operations.md
- Waiting, delays, callbacks, external systems, or polling -> see wait-operations.md
- Parallel execution, map operations, batch processing, or concurrency -> see concurrent-operations.md
- Error handling, retry strategies, saga pattern, or compensating transactions -> see error-handling.md
- Advanced error handling, timeout handling, circuit breakers, or conditional retries -> see advanced-error-handling.md
- Testing, local testing, cloud testing, test runner, or flaky tests -> see testing-patterns.md
- Deployment, CloudFormation, CDK, SAM, log groups, deploy, or infrastructure -> see deployment-iac.md
- Advanced patterns, GenAI agents, completion policies, step semantics, or custom serialization -> see advanced-patterns.md
- troubleshooting, stuck execution, failed execution, debug execution ID, execution history, execution error, why did my execution fail, execution timed out, callback not received, diagnose execution, or root cause execution -> see troubleshooting-executions.md
Quick Reference
Basic Handler Pattern
TypeScript:
import { withDurableExecution, DurableContext } from '@aws/durable-execution-sdk-js';
export const handler = withDurableExecution(async (event, context: DurableContext) => {
const result = await context.step('process', async () => processData(event));
return result;
});
Python:
from aws_durable_execution_sdk_python import durable_execution, DurableContext
@durable_execution
def handler(event: dict, context: DurableContext) -> dict:
result = context.step(lambda _: process_data(event), name='process')
return result
Python API Differences
The Python SDK differs from TypeScript in several key areas:
- Steps: Use
@durable_stepdecorator +context.step(my_step(args)), or inlinecontext.step(lambda _: ..., name='...'). Prefer the decorator for automatic step naming. - Wait:
context.wait(duration=Duration.from_seconds(n), name='...') - Exceptions:
ExecutionError(permanent),InvocationError(transient),CallbackError(callback failures) - Testing: Use
DurableFunctionTestRunnerclass directly - instantiate with handler, use context manager, callrun(input=...)
Invocation Requirements
Durable functions require qualified ARNs (version, alias, or $LATEST):
# Valid
aws lambda invoke --function-name my-function:1 output.json
aws lambda invoke --function-name my-function:live output.json
# Invalid - will fail
aws lambda invoke --function-name my-function output.json
IAM Permissions
Your Lambda execution role MUST have the AWSLambdaBasicDurableExecutionRolePolicy managed policy attached. This includes:
lambda:CheckpointDurableExecution- Persist execution statelambda:GetDurableExecutionState- Retrieve execution state- CloudWatch Logs permissions
Additional permissions needed for:
- Durable invokes:
lambda:InvokeFunctionon target function ARNs - External callbacks: Systems need
lambda:SendDurableExecutionCallbackSuccessandlambda:SendDurableExecutionCallbackFailure
Validation Guidelines
When writing or reviewing durable function code, ALWAYS check for these replay model violations:
- Non-deterministic code outside steps:
Date.now(),Math.random(), UUID generation, API calls, database queries must all be inside steps - Nested durable operations in step functions: Cannot call
context.step(),context.wait(), orcontext.invoke()inside a step function — usecontext.runInChildContext()instead - Closure mutations that won't persist: Variables mutated inside steps are NOT preserved across replays — return values from steps instead
- Side effects outside steps that repeat on replay: Use
context.loggerfor logging (it is replay-aware and deduplicates automatically)
When implementing or modifying tests for durable functions, ALWAYS verify:
- All operations have descriptive names
- Tests get operations by NAME, never by index
- Replay behavior is tested with multiple invocations
- Use
LocalDurableTestRunnerfor local testing
Security Considerations
- Checkpoint data encryption: Execution state is persisted automatically. Enable KMS encryption on associated CloudWatch Log Groups to protect checkpointed data at rest.
- Sensitive data in step results: Step return values are checkpointed and persisted. Do not return secrets, raw credentials, or PII from steps — store sensitive data in Secrets Manager or SSM Parameter Store and return references instead.
- Input validation: Validate and sanitize event payloads at the handler entry point before passing data to steps.
- Credential management: Retrieve secrets from AWS Secrets Manager or SSM Parameter Store within steps.
- Callback payload validation: Data received via
waitForCallbackoriginates from external systems — validate and sanitize before processing. - Logging: Avoid
DEBUGlog level in non-development environments as it may expose step results and execution state. Enable CloudWatch Logs encryption with KMS.
Resources
FAQ
What does the aws-lambda-durable-functions skill do?
Builds resilient, long-running, multi-step applications with AWS Lambda durable functions with automatic state persistence, retry logic, and orchestration for long-running executions. Covers the critical replay model, step operations, wait/callback patterns, error handling with saga pattern, testing with LocalDurableTestRunner. Triggers on phrases like lambda durable functions, durable execution, workflow orchestration, state machines, retry/checkpoint patterns, long-running stateful Lambda functions, saga pattern, human-in-the-loop callbacks, reliable serverless applications, context.step, context.wait, context.invoke, context.runInChildContext, withDurableExecution, DurableContext, UnrecoverableInvocationError, durable-execution-sdk, qualified ARN invocation, and durable handler replay.
How do I install aws-lambda-durable-functions?
Run npx skills add https://github.com/aws/agent-toolkit-for-aws --skill aws-lambda-durable-functions in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/aws-lambda-durable-functions/ (personal) or .claude/skills/aws-lambda-durable-functions/ (project).
Which AI agents can use aws-lambda-durable-functions?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is aws-lambda-durable-functions safe to install?
Security partners have reviewed it: Gen Agent Trust Hub passed; Socket passed; Snyk flagged items to review. As with any skill, read the SKILL.md and bundled scripts before installing.
Who maintains aws-lambda-durable-functions?
It is published by aws in aws/agent-toolkit-for-aws, and it is an official skill from the maker of the technology it covers. It has 5,794 recorded installs.
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