README.md

DynamodDB client in v2 vs v3

• This package contains backend code which performs create, delete, get, list and update operations on DynamoDB.
• It uses webpack to build single minimized bundle for each operation, and AWS CDK to deploy those bundles.

Table of Contents

• Set up
  • Create backend API
  • Test backend API
  • Clean resources
• Activities
  • Examine initial bundle size of lambda functions
  • Reduce bundle size by just importing dynamodb
  • Reduce bundle size further by using client from v3
  • Reduce bundle size even more by just importing specific commands in v3
• Correlation between lambda size and execution time
  • Traces for lambda which imports entire v2
  • Traces for lambda which imports specific client and command in v3
  • Comparison between v3 and v2 lambda duration

Set up

Ensure that you've followed pre-requisites from main README.

Create backend API

• yarn build:backend to build the package (runs ESLint and TypeScript).
• yarn cdk deploy to deploy your application (this operation might take time based on the state of your Cloudformation stack).

Test backend API

• Open the GatewayUrl link from CDK output from the console.
  • It'll be like: https://randomstring.execute-api.us-west-2.amazonaws.com/prod/
• Append notes in the URL.
  • It'll be like: https://randomstring.execute-api.us-west-2.amazonaws.com/prod/notes
• The contents of the notes DynamoDB table would be returned as JSON.
• If you don't see anything, that's because your table is likely empty! Add data manually or wait until you run the frontend.

Clean resources

• Note: Clean resources after you're done with all activities below, and you want to delete your cloudformation stack.
• yarn cdk destroy to delete your CloudFormation stack.

Activities

In this section, we're going to update the code to import DynamoDB Client in different ways and compare the bundle sizes of the resulting lambda functions.

Examine initial bundle size of lambda functions

• Login to AWS Lambda Console.

• The size of each lambda functions will be ~820 kB.

  Click to view image

  

• This happens because entire aws-sdk is bundled in the lambda in file dynamoDB.ts.

  import AWS from "aws-sdk";
  
  export default new AWS.DynamoDB();

Reduce bundle size by just importing dynamodb

• In v2, you can reduce the bundle size by doing dead-code elimination using tree shaking with a bundler like webpack.

• Just import the "aws-sdk/clients/dynamodb" in dynamoDB.ts, as shown in the diff below:

  -import AWS from "aws-sdk";
  +import DynamoDB from "aws-sdk/clients/dynamodb";
  
  -export default new AWS.DynamoDB();
  +export default new DynamoDB();

• Run yarn build:backend and yarn cdk deploy to build+deploy new code, and the size of lambda functions will reduce to ~90 kB!

  Click to view image

  

Reduce bundle size further by using client from v3

• Uninstall v2 by running the following command:

  • yarn remove aws-sdk

• Install dynamodb in v3 by running the following command:

  • yarn add @aws-sdk/client-dynamodb.

• Make the following change in dynamoDB.ts to import DynamoDB from v3.

  -import DynamoDB from "aws-sdk/clients/dynamodb";
  +import { DynamoDB } from "@aws-sdk/client-dynamodb";
  
  -export default new DynamoDB();
  +export default new DynamoDB({});

• The function calls v3 client return promises by default, so you've to remove .promise() from individual functions.

• For example, here's a diff for createNote.ts.

   try {
  +    // @ts-ignore
  -    await dynamoDB.putItem(params).promise();
  +    await dynamoDB.putItem(params);
     return success(params.Item);
   } catch (e) {
     return failure({ status: false });

• Run yarn build:backend and yarn cdk deploy to build+deploy new code, and the size of lambda functions will reduce to ~42 kB!

  Click to view image

  

Reduce bundle size even more by just importing specific commands in v3

• AWS JS SDK v3 has an option to import specific commands, thus reducing bundle size further!

• Make the following change in dynamoDB.ts to import DynamoDBClient from v3.

  -import { DynamoDB } from "@aws-sdk/client-dynamodb";
  +import { DynamoDBClient } from "@aws-sdk/client-dynamodb";
  
  -export default new DynamoDB({});
  +export default new DynamoDBClient({});

• Import and call just the PutCommand in createNote.ts for example:

  import crypto from "crypto";
  -import dynamoDB from "./libs/dynamoDB";
  +import dynamoDBClient from "./libs/dynamoDB";
  +import { PutItemCommand } from "@aws-sdk/client-dynamodb";
  import { success, failure } from "./libs/response";

    try {
  -    await dynamoDB.putItem(params);
  +    await dynamoDBClient.send(new PutItemCommand(params));
      return success(params.Item);
    } catch (e) {
      return failure({ status: false });

• Run yarn build:backend and yarn cdk deploy to build+deploy new code, and the size of lambda functions will reduce to ~23 kB!

  Click to view image

  

Correlation between lambda size and execution time

Here's how we find out correlation between lambda size and execution time:

• We get metrics by enabling Active tracing under AWS X-Ray for ListNotes lambda.
• The comparison is between original bundle which imports entire v2 with final bundle which imports specific command in v3.
• For testing, two fresh endpoints are created using Cloudformation and we visit <ENDPOINT>/Prod/notes in the browser.
• The cold start is the first hit post endpoint creation, and warm start is the second hit after ~3 seconds.

Traces for lambda which imports entire v2

Cold start

Click to view image

Warm start

Click to view image

Traces for lambda which imports specific client and command in v3

Cold start

Click to view image

Warm start

Click to view image

Comparison between v3 and v2 lambda duration

• A Cloudwatch event was written to trigger both lambdas every 20 mins and 18 values (in ms) for Duration of AWS::Lambda::Function were analyzed over 6 hours.

  	Average	Min	Max	Median	90th percentile
  entire v2	1171.5	1013	1431	1093.5	1193.39
  v3 command+client	735.22	693	786	738	775.6

• Another Cloudwatch event was written to trigger both lambdas every minute and 50 values (in ms) for Duration of AWS::Lambda::Function were analyzed.

  	Average	Min	Max	Median	90th percentile
  entire v2	117.82	85	178	116	139
  v3 command+client	116.22	83	176	115.5	136