One-to-One Relationships

Introduction

One-to-one (1:1) relationships always favor embedding in MongoDB. A user has one profile, an order has one shipping address, a product has one primary image. Put them in one document and skip the join forever.

Syntax reference

// 1:1 — embed
{
  _id: 1, name: "Ada",
  profile: { bio: "...", avatar: "https://..." }
}

Real-world use

User + profile is the textbook 1:1 case — always embedded.

Best practices

• Embed 1:1 every time unless the child is huge (> 1 MB) or rarely read.