migrations.js

const aws = require('aws-sdk')

module.exports = [
  async () => {...},
  async () => {...},
  async () => {...},
  async () => {
    const documentClient = new aws.DynamoDB.DocumentClient()
    const projects = await documentClient
      .scan({
        TableName: 'Projects',
        ProjectionExpression: 'id',
        FilterExpression: 'attribute_not_exists(creationTime)'
      })
      .promise()
      .then(({ Items }) => Items)

    return Promise.all(
      projects.map(({ id }) =>
        documentClient
          .update({
            TableName: 'Projects',
            Key: { id },
            UpdateExpression: 'set creationTime = :creationTime',
            ExpressionAttributeValues: {
              ':creationTime': Date.now()
            }
          })
          .promise()
      )
    )
  },
  async () => {...},
  async () => {...},
]