websocket-connection-topic.js

async subscribe({ topic, ttl }) {
   return dynamoDBClient
     .put({ 
        Item: {
         topic,
         connectionId: this.connectionId,
        ttl: typeof ttl === 'number' ? ttl : Math.floor(Date.now() / 1000) + 60 * 60 * 2,
       },
       TableName: process.env.TOPICS_TABLE,
     }).promise();
 }