aws api gateway & lambda: multiple endpoint/functions vs single endpoint

Question

I have an AWS api that proxies lamba functions. I currently use different endpoints with separate lambda functions:

api.com/getData --> getData
api.com/addData --> addData
api.com/signUp --> signUp

The process to manage all the endpoints and functions becomes cumbersome. Is there any disadvantage when I use a single endpoint to one lambda function which decides what to do based on the query string?

api.com/exec&func=getData --> exec --> if(params.func === 'getData') { ... }

Answer 1

It's perfectly valid to map multiple methods to a single lambda function and many people are using this methodology today as opposed to creating an api gateway resource and lambda function for each discrete method.

You might consider proxying all requests to a single function. Take a look at the following documentation on creating an API Gateway => Lambda proxy integration: http://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-set-up-simple-proxy.html

Their example is great here. A request like the following:

POST /testStage/hello/world?name=me HTTP/1.1
Host: gy415nuibc.execute-api.us-east-1.amazonaws.com
Content-Type: application/json
headerName: headerValue

{
    "a": 1
}

Will wind up sending the following event data to your AWS Lambda function:

{
  "message": "Hello me!",
  "input": {
    "resource": "/{proxy+}",
    "path": "/hello/world",
    "httpMethod": "POST",
    "headers": {
      "Accept": "*/*",
      "Accept-Encoding": "gzip, deflate",
      "cache-control": "no-cache",
      "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",
      "Content-Type": "application/json",
      "headerName": "headerValue",
      "Host": "gy415nuibc.execute-api.us-east-1.amazonaws.com",
      "Postman-Token": "9f583ef0-ed83-4a38-aef3-eb9ce3f7a57f",
      "User-Agent": "PostmanRuntime/2.4.5",
      "Via": "1.1 d98420743a69852491bbdea73f7680bd.cloudfront.net (CloudFront)",
      "X-Amz-Cf-Id": "pn-PWIJc6thYnZm5P0NMgOUglL1DYtl0gdeJky8tqsg8iS_sgsKD1A==",
      "X-Forwarded-For": "54.240.196.186, 54.182.214.83",
      "X-Forwarded-Port": "443",
      "X-Forwarded-Proto": "https"
    },
    "queryStringParameters": {
      "name": "me"
    },
    "pathParameters": {
      "proxy": "hello/world"
    },
    "stageVariables": {
      "stageVariableName": "stageVariableValue"
    },
    "requestContext": {
      "accountId": "12345678912",
      "resourceId": "roq9wj",
      "stage": "testStage",
      "requestId": "deef4878-7910-11e6-8f14-25afc3e9ae33",
      "identity": {
        "cognitoIdentityPoolId": null,
        "accountId": null,
        "cognitoIdentityId": null,
        "caller": null,
        "apiKey": null,
        "sourceIp": "192.168.196.186",
        "cognitoAuthenticationType": null,
        "cognitoAuthenticationProvider": null,
        "userArn": null,
        "userAgent": "PostmanRuntime/2.4.5",
        "user": null
      },
      "resourcePath": "/{proxy+}",
      "httpMethod": "POST",
      "apiId": "gy415nuibc"
    },
    "body": "{\r\n\t\"a\": 1\r\n}",
    "isBase64Encoded": false
  }
}

Now you have access to all headers, url params, body etc. and you could use that to handle requests differently in a single Lambda function (basically implementing your own routing).

As an opinion I see some advantages and disadvantages to this approach. Many of them depend on your specific use case:

• Deployment: if each lambda function is discrete then you can deploy them independently, which might reduce the risk from code changes (microservices strategy). Conversely you may find that needing to deploy functions separately adds complexity and is burdensome.
• Self Description: API Gateway's interface makes it extremely intuitive to see the layout of your RESTful endpoints -- the nouns and verbs are all visible at a glance. Implementing your own routing could come at the expense of this visibility.
• Lambda sizing and limits: If you proxy all -- then you'll wind up needing to choose an instance size, timeout etc. that will accommodate all of your RESTful endpoints. If you create discrete functions then you can more carefully choose the memory footprint, timeout, deadletter behavior etc. that best meets the needs of the specific invocation.