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Upgrade 1.x -> 2.x

See CHANGELOG for an overview of changes.

Version 2.x of Middy no longer supports Node.js versions 10.x. You are highly encouraged to move to Node.js 14, which support ES6 modules by default (export), optional chaining (?.) and nullish coalescing operator (??) natively.


  • In handler callback(err, reponse) have been removed for async/await support
    • return response to trigger after middleware stack
    • throw new Error(...) to trigger onError middleware stack
  • In middleware next(err) has been removed for async/await support
    • throw new Error(...) to trigger onError middleware stack
    • return reponse to short circuit any middleware stack and respond. v1.x currently throws an error when something is returned



Deprecated. Too generic and had low usage.

However, you can use the following if needed:

const { createHash } = require('crypto')

module.exports = (opts) => {
  const storage = {}
  const defaults = {
    calculateCacheId: async (event) => createHash('md5').update(JSON.stringify(event)).digest('hex'),
    getValue: async (key) => storage[key],
    setValue: async (key, value) => {
      storage[key] = value

  const options = { ...defaults, ...opts }
  let currentCacheKey

  const cacheMiddlewareBefore = async (request) => {
    const cacheKey = await options.calculateCacheId(request.event)
    const response = await options.getValue(cacheKey)
    if (response) {
      return response
    request.internal.cacheKey = cacheKey

  const cacheMiddlewareAfter = async (request) => {
    await options.setValue(request.internal.cacheKey, request.response)
  return {
    before: cacheMiddlewareBefore,
    after: cacheMiddlewareAfter


Deprecated. Too generic and had low usage. You can check out middy-rds as a possible alternative or example on building your own replacement.


No change


Deprecated. Only supported up to Node v10.


No change


Added new options to support more headers

  • methods
  • exposeHeaders
  • requestHeaders
  • requestMethods


Added in support to honour httpError.expose. Errors with statusCode >= 500 are no longer applied to response by default. Added new option to catch any non-http and statusCode >= 500 errors

  • fallbackMessage


No change


No change


No change


No change


No change


No change


No longer adds statusCode:500 when there is no response.


Remove extended option. Only uses qs as the parser, formally enabled by options {extended: true}.


No change


Now additionally logs response from the onError middleware stack


New middleware to fetch RDS credential used when connecting with IAM roles. This was built into db-manager.


No change


New middleware to fetch and respond to S3 Object Get request event.


Refactored, see documentation


No change


Replaced option sqs with AwsClient and added in more options for control.


Refactored, see documentation


New middleware to fetch assume role credentials.


Upgraded ajv and it's plugins to support JSON Schema Draft 2020-12 specification. Defaults were change because of this.

  • Plugin ajv-keywords removed from being included by default because it's quite a large package and usually only one keyword is used.
  • Plugin ajv-errors removed from included by default because it conflicts with ajv-i18n when dealing with custom messages for multiple languages


Deprecated. This was a work round for a missing feature in AWS Lambda. AWS added in the ability to use provisioned concurrency on 2019-12-03, removing the need for this work around.

However, you can use the following if needed:

  .before((request) => {
    if (request.event.source === 'serverless-plugin-warmup') {
      console.log('Exiting early via warmup Middleware')
      return 'warmup'

Upgrade 0.x -> 1.x

Independent packages structure

Version 1.x of Middy features decoupled independent packages published on npm under the @middy namespace. The core middleware engine has been moved to @middy/core and all the other middlewares are moved into their own packages as well. This allows to only install the features that are needed and to keep your Lambda dependencies small. See the list below to check which packages you need based on the middlewares you use:

Header normalization in http-header-normalizer

In Middy 0.x the httpHeaderNormalizer middleware normalizes HTTP header names into their own canonical format, for instance Sec-WebSocket-Key (notice the casing). In Middy 1.x this behavior has been changed to provide header names in lowercase format (e.g. sec-webSocket-key). This new behavior is more consistent with what Node.js core http package does and what other famous http frameworks like Express or Fastify do, so this is considered a more intuitive approach. When updating to Middy 1.x, make sure you double check all your references to HTTP headers and switch to the lowercase version to read them. All the middy core modules have been already updated to support the new format, so you should worry only about your userland code.

Node.js 10 and 12 now supported / Node.js 6 and 8 now dropped

Version 1.x of Middy no longer supports Node.js versions 6.x and 8.x as these versions have been dropped by the AWS Lambda runtime itself and not supported anymore by the Node.js community. You are highly encouraged to move to Node.js 12 or 10, which are the new supported versions in Middy 1.x.