HitCounterハンドラー

import { DynamoDB, Lambda } from 'aws-sdk';

export const handler: AWSLambda.APIGatewayProxyHandler = async (event) => {
  console.log('request:', JSON.stringify(event, undefined, 2));

  // create AWS SDK clients
  const dynamo = new DynamoDB();
  const lambda = new Lambda();

  // update dynamo entry for "path" with hits++
  await dynamo
    .updateItem({
      TableName: process.env.HITS_TABLE_NAME!,
      Key: { path: { S: event.path } },
      UpdateExpression: 'ADD hits :incr',
      ExpressionAttributeValues: { ':incr': { N: '1' } },
    })
    .promise();

  // call downstream function and capture response
  const resp = await lambda
    .invoke({
      FunctionName: process.env.DOWNSTREAM_FUNCTION_NAME!,
      Payload: JSON.stringify(event),
    })
    .promise();

  console.log('downstream response:', JSON.stringify(resp, undefined, 2));

  // return response back to upstream caller
  return JSON.parse(resp.Payload!.toString());
};