Embedding vs. References

Embedding (Denormalization)

Store related data in one document:

{ name: "Alice", orders: [{ product: "Widget" }] }

References (Normalization)

Store IDs pointing to other collections:

{ _id: "u1", name: "Alice" }
{ user_id: "u1", product: "Widget" }

When to Embed

• Data accessed together
• One-to-few relationships

When to Reference

• Large sub-documents
• Many-to-many relationships