Schema Validation

Introduction

Schema validation in MongoDB lets you enforce a JSON Schema at the database layer. You get the flexibility of NoSQL during development and the safety of strict types when you're ready for production.

Syntax reference

db.runCommand({
  collMod: "orders",
  validator: { $jsonSchema: {
    required: ["userId", "total", "status"],
    properties: {
      userId: { bsonType: "objectId" },
      total:  { bsonType: "decimal", minimum: 0 },
      status: { enum: ["pending","paid","shipped","cancelled"] }
    }
  }},
  validationLevel: "moderate"
});

Real-world use

Teams add validators as soon as the schema stabilizes — usually right after the first production launch.

Best practices

• Use validationLevel: 'moderate' to grandfather old docs.
• Pair with TypeScript types for end-to-end safety.