How to keep track of a private messaging system using MongoDB?

Question

Take facebook\'s private messaging system where you have to keep track of sender and receiver along w/ the message content. If I were using MySQL I would have multiple table

Answer 1

Your Db Schema Should be like this->

let chatImages = {
    original  : {type:String,required:true,trim:true},
    thumbnail : {type:String,required:true,trim:true}
};

let Chats = new Schema({
    CommonId  : {type: String, trim: true, index: true, unique: true,sparse: true},
    senderId   : {type: Schema.Types.ObjectId,index: true,required:true,ref:'User'},
    receiverId : {type: Schema.Types.ObjectId,index: true,required:true,ref:'User'},
    messageId  : {type: String, trim: true, index: true, unique: true,sparse: true},
    isDeliver  : {type: Boolean, default: false},
    isSent     : {type: Boolean, default: true},
    chatType   : {
                 type: String,required:true,enum: [
                 Config.APP_CONSTANTS.DATABASE.CHAT_TYPE.TEXT,
                 Config.APP_CONSTANTS.DATABASE.CHAT_TYPE.IMAGE
                 ],default:Config.APP_CONSTANTS.DATABASE.CHAT_TYPE.TEXT},
    text       : {type: String, trim: true, index: true,sparse: true},
    sentAt     : {type:Number, default: Date.now,index:true,required: true},
    chatImage  : {type:chatImages},
});

CommonId is very Important if you want the screen like whatsApp where you can see the persons with whom you chat. 1)It Make Grouping very easy(with $groupBy).

You can Generate CommonId by just Compare between receiverId and SenderId which is ascending put it CommonId

I think its a nice Explaination