C100DEV Data Modeling Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  It allows a single query to retrieve all related items across different types.

  Why this is correct

  Because all polymorphic entities reside in the same collection, a single find operation can return all relevant items, regardless of their specific type. This avoids running multiple queries against different collections and merging results in the application, which simplifies code and reduces database round-trip times for complex operations.

• ✗

  It enforces strict schema validation for all documents within the collection.

  Why it's wrong here

  The polymorphic pattern is inherently flexible. While you can use JSON Schema validation, the pattern itself is about accommodating variation. Claiming it enforces strict schema validation for all documents is contradictory to the purpose of polymorphism, which is designed to handle differing structures across documents within the same collection.

• ✓

  It simplifies management by grouping related entities into one collection.

  Why this is correct

  Grouping similar entities—even with varying schemas—into one collection reduces the number of collections that need maintenance, backup, and index management. It provides a more organized data model that aligns with how application code handles inheritance or varied object types, making the database easier to manage and query.

• ✗

  It automatically increases the write throughput of the database cluster.

  Why it's wrong here

  Write throughput is governed by factors like indexing, lock contention, and hardware, not the specific schema pattern. While polymorphism organizes data, it does not provide an inherent performance boost to write operations. In fact, complex indexes on polymorphic collections might even slightly decrease write throughput under high load.

• ✗

  It allows for unlimited document size by splitting fields across collections.

  Why it's wrong here

  The polymorphic pattern has nothing to do with bypassing the 16MB BSON document limit. It is about schema flexibility. Splitting fields across collections is a form of normalization, not polymorphism. Documents still must adhere to the 16MB limit, and this pattern does not provide a mechanism to circumvent it.