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MongoDB Schema Design: Embedded vs Referenced with Examples

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MongoDB schema design example in Visualeaf, comparing embedded data inside a users document with referenced data between users and payments.

When you design a MongoDB database, one of the first choices is this:<br>Should this data stay inside the same document, or should it live in another collection?<br>That is the difference between embedding and referencing .<br>Embedding means the data is stored inside the document.<br>Referencing means the data is stored in another collection and connected with an _id.<br>That’s the main difference.<br>Let’s use a simple database called streaming_platform_db.<br>It has collections like users, movies, series, episodes, payments, ratings, watch_history, and activity_logs.<br>The database works like a basic streaming platform.<br>A user can have a subscription, profiles, and devices. The same user can also make payments, watch content, rate movies, and create activity logs.<br>That makes this database a good example because it uses both embedded data and referenced data.<br>Visual Schema Design<br>In Visualeaf, I generated a schema diagram for the streaming_platform_db database.<br>This makes the structure easier to understand because I can see the collections and their relationships in one place.<br>VisuaLeaf schema diagram for streaming_platform_db, showing embedded fields and referenced collections.For example, the users collection has fields like:<br>subscription<br>profiles<br>devicesThese fields are stored inside each user document.<br>That means they are embedded .<br>But other collections, like payments, ratings, watch_history, and activity_logs, are connected to users with user_id.<br>That means they are referenced .<br>So the diagram shows the main idea very clearly:<br>Some data lives inside a document.<br>Some data lives in another collection and points back with an ID.<br>A Quick Example in Mongo Shell<br>To make this easier to see, here is a small example from the users collection.<br>In this document, subscription, profiles, and devices are stored inside the user document.<br>That means they are embedded .<br>db.users.insertOne({<br>full_name: "Oliver Smith",<br>email: "oliver.smith@streaming.test",<br>country: "UK",<br>city: "London",

subscription: {<br>plan: "standard",<br>status: "active"<br>},

profiles: [<br>profile_name: "Oliver",<br>type: "adult",<br>preferences: {<br>favorite_genres: ["Action", "Sci-Fi"],<br>subtitles: ["en"]<br>},<br>profile_name: "Kids",<br>type: "kids",<br>kids_mode: true<br>],

devices: [<br>type: "laptop",<br>os: "Windows 11"<br>});After creating this document in Mongo Shell, Visualeaf makes the embedded structure easier to see. The fields are inside the users document, not in separate collections.<br>Embedded data in the users collection. The subscription, profiles, preferences, and devices are stored inside the same user document.Now compare that with referenced data.<br>Payments are not stored inside the user document. They live in a separate collection and point back to the user with user_id.<br>db.payments.insertOne({<br>user_id: ObjectId("USER_ID_HERE"),<br>amount: 12.99,<br>currency: "EUR",<br>status: "paid",<br>paid_at: new Date()<br>});Here, user_id connects the payment to the user.<br>That is a reference .<br>Visualeaf schema view showing the reference between users and payments through user_id.One important thing to know: a MongoDB reference is not the same as a SQL foreign key.<br>In SQL, a foreign key can enforce the relationship between two tables.<br>In MongoDB, user_id is just a field that stores another document’s _id.<br>MongoDB does not automatically check that the user exists.<br>So the difference from the main diagram is simple:<br>users.devices // embedded<br>users.profiles // embedded<br>users.subscription // embedded

payments.user_id // referenced<br>ratings.user_id // referenced<br>watch_history.user_id // referenced<br>activity_logs.user_id // referencedEmbed data when it belongs inside the document.<br>Reference data when it should stay in another collection.<br>Where embedding fits<br>Embedding is a good choice when your data is associated with one primary...