Lambda Event Payloads by Example

Direct Invocation

In case the official docs are not clear about this, here are the facts:

  • If you invoke a Lambda function directly using SDK or CLI, you pass args as a JSON string, and you get the result serialized as a JSON string
  • Your function receives the args directly as its first argument, whatever you pass in will directly pass onto your function (parsed into native data format)
  • This is notably different than the API Gateway integration where an event parameter is used, and the payload be reside in event.body in its JSON string form; also when you send data back, you don’t need to serialize it as the integration will do it for you

API Gateway

There are two versions of payload.

Version 1

let event = {
  "body": "{\"message\": \"hello world\"}",
  "resource": "/{proxy+}",
  "path": "/path/to/resource",
  "httpMethod": "POST",
  "isBase64Encoded": false,
  "queryStringParameters": {
    "foo": "bar"
  "pathParameters": {
    "proxy": "/path/to/resource"
  "stageVariables": {
    "baz": "qux"
  "headers": {
    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8",
    "Accept-Encoding": "gzip, deflate, sdch",
    "Accept-Language": "en-US,en;q=0.8",
    "Cache-Control": "max-age=0",
    "CloudFront-Forwarded-Proto": "https",
    "CloudFront-Is-Desktop-Viewer": "true",
    "CloudFront-Is-Mobile-Viewer": "false",
    "CloudFront-Is-SmartTV-Viewer": "false",
    "CloudFront-Is-Tablet-Viewer": "false",
    "CloudFront-Viewer-Country": "US",
    "Host": "",
    "Upgrade-Insecure-Requests": "1",
    "User-Agent": "Custom User Agent String",
    "Via": "1.1 (CloudFront)",
    "X-Amz-Cf-Id": "cDehVQoZnx43VYQb9j2-nvCh-9z396Uhbp027Y2JvkCPNLmGJHqlaA==",
    "X-Forwarded-For": ",",
    "X-Forwarded-Port": "443",
    "X-Forwarded-Proto": "https"
  "requestContext": {
    "accountId": "123456789012",
    "resourceId": "123456",
    "stage": "prod",
    "requestId": "c6af9ac6-7b61-11e6-9a41-93e8deadbeef",
    "requestTime": "09/Apr/2015:12:34:56 +0000",
    "requestTimeEpoch": 1428582896000,
    "identity": {
      "cognitoIdentityPoolId": null,
      "accountId": null,
      "cognitoIdentityId": null,
      "caller": null,
      "accessKey": null,
      "sourceIp": "",
      "cognitoAuthenticationType": null,
      "cognitoAuthenticationProvider": null,
      "userArn": null,
      "userAgent": "Custom User Agent String",
      "user": null
    "path": "/prod/path/to/resource",
    "resourcePath": "/{proxy+}",
    "httpMethod": "POST",
    "apiId": "1234567890",
    "protocol": "HTTP/1.1"

Version 2

let event = {
  version: '2.0',
  routeKey: '$default',
  rawPath: '/my/path',
  rawQueryString: 'parameter1=value1¶meter1=value2¶meter2=value',
  cookies: [ 'cookie1', 'cookie2' ],
  headers: {
    'Header1': 'value1',
    'Header2': 'value2'
  queryStringParameters: { parameter1: 'value1,value2', parameter2: 'value' },
  requestContext: {
    accountId: '123456789012',
    apiId: 'api-id',
    authorizer: { jwt: {
        claims: {'claim1': 'value1', 'claim2': 'value2'},
        scopes: ['scope1', 'scope2']
    domainName: '',
    domainPrefix: 'id',
    http: {
      method: 'POST',
      path: '/my/path',
      protocol: 'HTTP/1.1',
      sourceIp: 'IP',
      userAgent: 'agent'
    requestId: 'id',
    routeKey: '$default',
    stage: '$default',
    time: '12/Mar/2020:19:03:58 +0000',
    timeEpoch: 1583348638390
  body: 'Hello from Lambda',
  pathParameters: {'parameter1': 'value1'},
  isBase64Encoded: false,
  stageVariables: {'stageVariable1': 'value1', 'stageVariable2': 'value2'}


  "Records": [
      "messageId": "19dd0b57-b21e-4ac1-bd88-01bbb068cb78",
      "receiptHandle": "MessageReceiptHandle",
      "body": "Hello from SQS!",
      "attributes": {
        "ApproximateReceiveCount": "1",
        "SentTimestamp": "1523232000000",
        "SenderId": "123456789012",
        "ApproximateFirstReceiveTimestamp": "1523232000001"
      "messageAttributes": {},
      "md5OfBody": "7b270e59b47ff90a553787216d55d91d",
      "eventSource": "aws:sqs",
      "eventSourceARN": "arn:aws:sqs:us-east-1:123456789012:MyQueue",
      "awsRegion": "us-east-1"