我使用的是聚合查询，多表联查，当访问过大当时候错误次数很高，请问如何解决？以下是具体代码

 const wxContext = cloud.getWXContext()
  const db = cloud.database()

  const $ = db.command.aggregate
  return db.collection('activity')
    .aggregate()
    .match({
      _openid: wxContext.OPENID
    })
    .lookup({
      from: 'apply',
      localField: '_id',
      foreignField: 'atcId',
      as: 'atcList',
    })
    .project({
      userInfo: 1,
      title: 1,
      content: 1,
      type:1,
      createTime:1,
      isOpen:1,
      atcTotal: $.size('$atcList')
    })
    .sort({
      createTime: -1,
    })
    .end()