AWS Lambda Durable Functions

What it does

When your agent uses it

• Phrases like lambda durable functions
• Durable execution
• Workflow orchestration
• Retry/checkpoint patterns

Example prompts

• “Use the aws-lambda-durable-functions skill to build resilient, long-running, multi-step applications with AWS Lambda durable functions with…”
• “/aws-lambda-durable-functions”

Requirements

• Python 3

Workflow steps

6 steps, taken from the first numbered list in SKILL.md.

1. 1Durable execution must be enabled at function creation time — it cannot be retrofitted. A new Lambda function must be created with durable…
2. 2Durable functions must be invoked with a qualified ARN — a specific version, an alias, or the literal $LATEST suffix. An unqualified…
3. 3Durable operations cannot be nested. You cannot call context.step(), context.wait(), or context.invoke() from inside another step's…
4. 4All non-deterministic code must run inside steps. Date.now(), Math.random(), UUID generation, API calls, and database queries outside a…
5. 5Closure mutations are lost on replay - return values from steps
6. 6Side effects outside steps repeat - use context.logger (replay-aware)

What it can do on your machine

Read from SKILL.md and the folder at commit 188af2f. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Shell commands in SKILL.md call:

  • aws

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • docs.aws.amazon.com
  • github.com

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

AWS Lambda Durable Functions loads about 2.3k tokens when it runs, and up to ~31k if it reads all its reference files. Until then it costs about 207 tokens; SKILL.md has 786 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~207

When it runs · the whole SKILL.md, loaded when a task matches

~2.3k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~31k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from aws/agent-toolkit-for-aws at commit 188af2f, republished under its Apache-2.0 licence (© aws). 786 words, ~2,267 tokens.

name

aws-lambda-durable-functions

description

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.

version

1

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;
});

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

# 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

© aws, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 11 other files (references) in skills/specialized-skills/serverless-skills/aws-lambda-durable-functions of aws/agent-toolkit-for-aws.

• SKILL.md
• references/advanced-error-handling.md
• references/advanced-patterns.md
• references/concurrent-operations.md
• references/deployment-iac.md
• references/error-handling.md
• references/getting-started.md
• references/replay-model-rules.md
• references/step-operations.md
• references/testing-patterns.md
• references/troubleshooting-executions.md
• references/wait-operations.md

Open the folder on GitHubat commit 188af2f