Example of SQL & MongoDB way DB design

post.model.js

/*
 * SQL way design
 * Comment schema is separate from post schema
 * If you have to perfrom critical operations on comments then this is suitable option,
 * but if you will be performing simple operations like CRUD, you can keep comments in post schema
 * Con: You have to write seprate query to fetch comments and it will cause extra burden
 */

/*
 * Post Schema
 */
const postSchema = new Schema({
  createdBy: {
    type: Schema.Types.ObjectId,
    ref: "User",
  },
  heading: String,
  description: String,
});

/*
 * Comment Schema
 */
const commentSchema = new Schema({
  createdBy: {
    type: Schema.Types.ObjectId,
    ref: "User",
  },
  post: {
    type: Schema.Types.ObjectId,
    ref: "Post",
  },
  text: String,
});

/*
 * MongoDB way design
 * Comment schema is combined into post schema
 * It will be difficult to perform critical operations on comments
 * This is best suitable way, if you will be performing simple operations on comments like CRUD
 * Pro: You can get everything in one single query
 */

/*
 * Post Schema with comments
 */
const postSchema = new Schema({
  createdBy: {
    type: Schema.Types.ObjectId,
    ref: "User",
  },
  heading: String,
  description: String,
  comments: [
    {
      createdBy: {
        type: Schema.Types.ObjectId,
        ref: "User",
      },
      text: String,
    },
  ],
});