DP-900 Describe core data concepts 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.

• ✗

  Enforcing referential integrity

  Why it's wrong here

  Referential integrity is implemented in relational databases through foreign key constraints that guarantee a child record always points to an existing parent record. NoSQL databases typically avoid such constraints because they favor denormalized data models, where related data is embedded or duplicated rather than referenced. In a distributed system, enforcing foreign keys across partitions would require expensive coordination and would undermine availability and write performance. Therefore, this is a capability of relational systems, not a benefit of NoSQL.

• ✗

  Support for complex joins

  Why it's wrong here

  Relational databases use SQL joins to combine data across multiple tables on the fly, which is a fundamental query pattern that NoSQL databases do not natively support for complex, ad-hoc relationships. Instead, NoSQL models are designed around pre-joined or denormalized storage, such as embedding related documents within a single record, to avoid the need for server-side joins. When joins are needed in NoSQL, they must be implemented in application code or performed through limited, client-side queries, which is inefficient at scale. Hence, complex joins are a relational strength, not a NoSQL benefit.

• ✓

  Horizontal scalability

  Why this is correct

  Horizontal scalability is a core design goal of NoSQL databases, which distribute data and query load across many commodity servers using sharding and consistent hashing. Unlike a single relational server that must be upgraded vertically (scale-up), NoSQL systems can add more nodes dynamically to handle increased traffic and data volume (scale-out). Azure Cosmos DB, for example, automatically splits partitions based on partition keys and can elastically scale throughput and storage across regions. This makes horizontal scalability a primary advantage for global, high-velocity applications.

• ✓

  Schema flexibility

  Why this is correct

  Schema flexibility means NoSQL databases allow each record to have a different set of attributes, so developers can evolve data structures without executing ALTER TABLE migrations or locking the database. This is especially valuable for applications with heterogeneous data, rapid changes in requirements, or ingestion of semi-structured JSON documents where fields may be optional or vary over time. Because there is no fixed relational schema, adding a new field does not require updating existing records or coordinating a migration across a busy production system. Thus, schema flexibility is an important benefit of NoSQL, but it is distinct from scalability.

• ✗

  Full ACID transactions across multiple documents

  Why it's wrong here

  Full ACID transactions across multiple documents are not a general benefit of NoSQL; many NoSQL databases relax cross-document atomicity and isolation in favor of eventual consistency and partition tolerance. While some NoSQL systems, including Azure Cosmos DB, now offer multi-item transactions within a single logical partition, these transactions are limited in scope and do not span arbitrary partitions or collections as easily as relational transactions. Relational databases enforce strict ACID guarantees globally, including serializable isolation and rollback across tables, which NoSQL often sacrifices. Therefore, this option describes a feature that is more characteristic of relational platforms, not a core NoSQL benefit.

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