Idempotency Middleware for Middy

Make AWS Lambda Functions Idempotent using Middy

In programming, idempotency refers to the capacity of an application or component to identify repeated events and prevent duplicated, inconsistent, or lost data. Making your AWS Lambda function idempotent requires designing your function logic to treat duplicated events correctly.

Idempotent function logic can help to reduce the following issues:

Unnecessary API calls
Code processing time
Data inconsistency
Throttles
Latency

Middy is a middleware framework that allows you to simplify your AWS Lambda code when using Node.js. This middleware aims to replicate the AWS Lambda Powertools idempotency utility built in Python.

Other sources to learn about idempotency:

Other idempotency projects for Middy:

middy-idempotent - Uses ioredis and Upstash

Install

To install this middleware you can use NPM:

npm install --save middy-idempotency

Requires @middy/core >= 2.0.0

Usage

middy-idempotency requires a persistence store to save the current status of an AWS Lambda execution. Currently, only DynamoDB is supported as a persistence store.

const middy = require('@middy/core')
const idempotency = require('middy-idempotency')

const DynamoDbPersistenceLayer = require('middy-idempotency/persistence/dynamodb')

const processEvent = async (event, context) => {
  return {
    statusCode: 200,
    body: JSON.stringify({
      message: 'hello world',
    }),
  }
}

const dynamodb = new DynamoDbPersistenceLayer({
  tableName: 'myIdempotencyTable',
})

const lambdaHandler = middy(processEvent).use(idempotency({ PersistenceStore: dynamodb }))

module.exports = { lambdaHandler }

TODO

Improve documentation
Add in-memory cache
Add payload validation
Add more advanced customization
Add other persistence stores (i.e. Redis)
Convert to TypeScript for type checking

Contributing

Feel free to fork and make a PR for any enhancements or new features!

MIT License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.