How to Correctly Model Relationships in NoSQL Databases Like MongoDB

Developers migrating from SQL to NoSQL databases like MongoDB often mistakenly replicate relational patterns, splitting data across multiple collections and manually writing joins in application code. Unlike SQL, NoSQL document databases have no foreign key constraints, no cascade deletes, and limited native join support, requiring a fundamentally different design approach. The core decision in NoSQL modeling is whether to embed related data directly inside a parent document or reference it via a stored ID in a separate collection. Data should be shaped around known query patterns rather than normalized into isolated tables, as a single well-structured document can return all needed data in one read. Key relationship patterns — one-to-one, one-to-many, and many-to-many — each have distinct embedding or referencing strategies that apply across MongoDB, DynamoDB, Cassandra, and Cosmos DB.