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// 1. Create a DynamoDB table const dynamoTable = new dynamodb.Table(this, 'DynamoTable', { partitionKey: { name: 'id', type: dynamodb.AttributeType.STRING }, billingMode: dynamodb.BillingMode.PAY_PER_REQUEST, removalPolicy: RemovalPolicy.DESTROY, stream: dynamodb.StreamViewType.NEW_AND_OLD_IMAGES, }) // 2. Create a Lambda function that will be triggered by the DynamoDB stream // you can see how to create lambda functions in typescript in the following link: // https://www.codewithyou.com/blog/writing-typescript-lambda-in-aws-cdk const fn = new NodejsFunction(this, 'Handler', { entry: './lambda/index.ts', handler: 'main', runtime: lambda.Runtime.NODEJS_14_X, architecture: lambda.Architecture.ARM_64, bundling: { externalModules: ['aws_sdk'], minify: true, }, }) // 3. currently, aws cdk is not yet support filtering event sources // https://github.com/aws/aws-cdk/issues/17874 // So, we need create a source mapping to map the DynamoDB table to the Lambda function const sourceMapping = new lambda.EventSourceMapping(this, 'SourceMapping', { startingPosition: lambda.StartingPosition.TRIM_HORIZON, batchSize: 1, // only process one record at a time target: fn, // the lambda function to trigger eventSourceArn: dynamoTable.tableStreamArn, // the DynamoDB stream to read from bisectBatchOnError: true, // if the Lambda function fails, split the batch into two retryAttempts: 3, // retry 3 times if the Lambda function fails }) // grant the function stream access to the DynamoDB table dynamoTable.grantStreamRead(fn) // filter the event source mapping to only process records with the specified event type (in this case, "INSERT") const cfnSourceMapping = sourceMapping.node.defaultChild as lambda.CfnEventSourceMapping // get the underlying CloudFormation resource cfnSourceMapping.addPropertyOverride('FilterCriteria', { Filters: [ { Pattern: JSON.stringify({ eventName: ['INSERT'], // only process INSERT events }), }, ], })