I have built a social network which has a news feed, too. Here is how I did it.

Basically, you have 2 methods to built a newsfeed:

1. Fanout on write (push) method
2. Fanout on read (pull) method

Fanout on write

First, you will need another collection:

const Newsfeed = new mongoose.model('newsfeed', {  owner: {type: mongoose.Types.ObjectId, required: true},  post: {type: mongoose.Types.ObjectId, required: true}});

When a user post something:

1. Get n follower
2. Push (fanout) this post to n follower

When a user get a feed:

1. Get from Newsfeed collection

Example:

router.post('/tweet', async (req, res, next) => {  let post = await Post.create({});  let follows = await Follow.find({target: req.user.id}).exec();  let newFeeds = follows.map(follow => {    return {      user: follow.user,      post: post.id    }  });  await Newsfeed.insertMany(newFeeds);});router.get('/feed', async (req, res, next) => {  let feeds = await Newsfeed.find({user: req.user.id}).exec();});

Fanout on read

When a user post something:

1. Save

When a user get feed

1. Get n following
2. Get posts from n following

Example

router.post('/tweet', async (req, res, next) {  await Post.save({});});router.get('/feeds', async (req, res, next) {  let follows = await Follow.find({user: req.user.id}.exec();  let followings = follows.map(follow => follow.target);  let feeds = await Post.find({user: followings}).exec();});

You don't need Redis or pub/sub to implement a newsfeed. However, in order to improve the performance, you may need Redis to implement some kind of cache for this.

For more information or advance technique, you may want to take a look at this.

User Schema :

var mongoose = require('mongoose');var Schema = mongoose.Schema;const userSchema = new Schema({     name:{type:String},     email: { type: String, unique: true, lowercase: true},  },{    collection: 'User'  });var User = module.exports = mongoose.model('User', userSchema);

Follow Schema :

var mongoose = require('mongoose');var Schema = mongoose.Schema;var followSchema = new Schema(    {        follow_id: { type: Schema.Types.ObjectId, required: true, ref: 'User'  },        leader_id: { type: Schema.Types.ObjectId, required: true, ref: 'User' }    },{        collection:'Follow'    }); var Follow = module.exports = mongoose.model('Follow', followSchema);

Post Schema :

 var mongoose = require('mongoose'); var Schema = mongoose.Schema;var postSchema = new Schema({  creator: { type: Schema.Types.ObjectId, ref: 'User' }  body: {type: String , required:true},  created_at :{type:Date , default:Date.now}},{    collection:'Post'  });var Post = module.exports = mongoose.model('Post', postSchema);

Now Suppose you have 3 users in User collection :

{ _id: ObjectID('5a2ac68d1413751391111111') ,name:'John' , email:'john@gmail.com'}{ _id: ObjectID('5a2ac68d1413751392222222') ,name:'Morgan' , email:'morgan@yahoo.com'}{ _id: ObjectID('5a2ac68d1413751393333333') ,name:'Emily' , email:'emily@outlook.com'}

Now John Follows Morgan and Emily :

so in Follow collection there are two records

1) follow_id = John's ID and leader_id = Morgan's ID

2) follow_id = John's ID and leader_id = Emily's ID

{   _id: ObjectID('5a2ac68d141375139999999'),  follow_id : ObjectID('5a2ac68d1413751391111111'),  leader_id : ObjectID('5a2ac68d1413751392222222')},  {     _id: ObjectID('5a2ac68d1413751393333333'),    follow_id : ObjectID('5a2ac68d1413751391111111'),    leader_id : ObjectID('5a2ac68d1413751393333333')  }

Now if you want to get User's Following :

app.get('/following/:user_id',function(req,res){      var userid=req.params.user_id;      Follow.find({follow_id:mongoose.mongo.ObjectID(userid)})      .populate('leader_id')      .exec(function(err,followings){       if(!err && followings){           return res.json({followings:followings});       }      });});

for getting User's Followers :

   app.get('/followers/:user_id',function(req,res){      var userid=req.params.user_id;      Follow.find({leader_id:mongoose.mongo.ObjectID(userid)})      .populate('follow_id')      .exec(function(err,followers){       if(!err && followers){           return res.json({followers:followers});       }      });});

npm install redis

in your app.js :

var redis = require('redis');var client = redis.createClient();

When one user create post :

app.post('/create_post',function(req,res){       var creator=new mongoose.mongo.ObjectID(req.body.creator);       var postbody=req.body.body;       async.waterfall([          function(callback){          // find followers of post creator          Follow.find({leader_id:creator})              .select({ "follow_id": 1,"leader_id":0,"_id": 0})              .exec(function(err,followers){                      if(!err && followers){                       callback(null,followers);                      }              });         },        function(followers, callback){          // saving the post         var post=new Post({            creator: creator,            body: postbody         });          post.save(function(err,post){             if(!err && post){   // adding newly created post id to redis by key userid , value is postid                for(var i=0;i<followers.length;i++){                   client.sadd([followers[i].follow_id,post.id]);                }                 callback(null,post);             }         });         }   ], function (err, result) {             if(!err && result){                return res.json({status:"success",message:"POST created"});             }       });    });

Now For Getting User NewsFeed :

1) first get array of postid from redis key of userid

2) loop through postid and get post from mongo

Function for get newsfeed by userid :

app.get('/newsfeed/:user_id',function(req,res){    var userid=req.params.user_id;    client.smembers(userid,function(err, reply) {        if(!err && reply){            console.log(reply);            if(reply.length>0){               var posts=[];               for(var i=0;i<reply.length;i++){                  Post.findOne({_id:new mongoose.mongo.ObjectID(reply[i])}).populate('creator').exec(function(err,post){                         posts.push(post);      });               }              return res.json({newsfeed:posts});            }else{              // No News Available in NewsFeed            }        }    });});

Here we have use redis to store [userid,array of postids] for newsfeed ,but if you dont want to use redis than just use below Newsfeed Model and store user_id and post_id for newly created post and then display it.

NewsFeed Schema :

 var mongoose = require('mongoose'); var Schema = mongoose.Schema;var newsFeedSchema = new Schema({  user_id: {type: Schema.Types.ObjectId, refer:'User' , required:true}  post_id: {type: Schema.Types.ObjectId, refer:'Post' , required:true},},{    collection:'NewsFeed'  });var NewsFeed = module.exports = mongoose.model('NewsFeed', newsFeedSchema);

Helpful link for Redis : https://www.sitepoint.com/using-redis-node-js/

for Async : https://caolan.github.io/async/docs.html#