https://blog.battlefy.com/how-not-to-blow-up-the-production-database-424c162dccc6 solution

001 apex-legends-score-report.js

type ApexLegendsGameResult = {
  teamID: string,
  placement: number,
  kills: number
};
application.post('/apex-legends/:gameID/report-score', async ({params: {gameID}, body}, res) => {
  await db.collection('apexLegendsGames').updateOne({
    _id: gameID
  }, {
    $set: {
      state: 'completed',
      results: body as ApexLegendsGameResult[]
    }
  });
  
  // signal to view service this document was updated
  await views.documentUpdated({
    collection: 'apexLegendsGames',
    _id: gameID
  });
  
  return res.sendStatus(204);
});

002 view-service.js

const views = [
  {
    name: 'team stats table',
    // dependencies resolve to the view params, in this case tournamentID
    dependencies: {
      async apexLegendsGames(gameID) {
        const {tournamentID} = await db.collection('apexLegendsGames').findOne({
          _id: gameID
        });
        return tournamentID;
      },
      async teams(teamID) {
        const {tournamentID} = await db.collection('teams').findOne({
          _id: teamID
        });
        return tournamentID;
      }
    },
    
    async generate(tournamentID) {
      const games = await db.collection('apexLegendsGames').find({
        state: 'completed',
        tournamentID
      })
        .toArray();
      let totalKillsByTeamID = 0;
      for (const {results} of games) {
        for (const {teamID, kills} of results) {
          totalKillsByTeamID[teamID] = totalKillsByTeamID[teamID] || {};
          totalKillsByTeamID[teamID] += kills;
        }
      }
  

      const teams = await db.collection('teams').find({
        tournamentID
      })
        .toArray();
      const teamByID = _.keyBy(teams, '_id');
      
      await db.collection('teamStats').bulkWrite(teams.map(({_id: teamID}) => ({
        updateOne: {
          filter: {
            tournamentID,
            teamID
          },
          update: {
            $set: {
              teamName: teamByID[teamID].name,
              totalKills: totalKillsByTeamID[teamID],
              averageKills: totalKillsByTeamID[teamID] / results.length
            }
          },
          upsert: true
        }
      })));
    }
  }
];
export async documentUpdated({collection, _id}) {
  for (const {dependencies, generate} of views) {
    const dependencyResolver = dependencies[collection];
    if (dependencyResolver) {
      await generate(dependencyResolver(_id));
    }
  }
}

003 tournament-team-stats.js

application.get('/tournament/:tournamentID/team-stats', ({params: {tournamentID}, query: {sort, page}}, res) => {
  const teamsPerPage = 10;
  const pageIndex = page * teamsPerPage;
  const page = db.collection('teamStats').find({
    tournamentID
  })
    .sort({
      [sort]: 1
    })
    .skip(pageIndex)
    .limit(teamsPerPage)
    .toArray();
  
  return res.send(page);
});