AZ-305 Design data storage solutions 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.

• ✗

  Azure Table Storage

  Why it's wrong here

  Azure Table Storage provides no native change data capture capability; it is a schemaless NoSQL key-value store whose clients perform direct point reads and writes with optimistic concurrency, but there is no built-in change feed, transaction log reader, or CDC interface. To detect changes you would have to poll timestamp properties or maintain a separate audit table, which is neither native nor transactionally consistent. It is therefore not a service that offers CDC out of the box.

• ✓

  Azure Cosmos DB

  Why this is correct

  Azure Cosmos DB is a correct answer because it exposes a native change feed directly from the container, implemented as an append-only, ordered per logical partition log that captures item inserts, updates, and deletes. This change feed is consumed via the Cosmos DB SDK, Azure Functions trigger, or the Change Feed Processor library, delivering at-least-once semantics and automatic paging. This is a first-class CDC facility for a multi-model NoSQL database, distinct from a SQL-based CDC implementation.

• ✗

  Azure Cache for Redis

  Why it's wrong here

  Azure Cache for Redis is an in-memory data store used for caching, session state, and transient messaging, not a durable database with a change capture log. Its AOF or RDB persistence mechanisms exist solely for recovery after restart and do not provide an external stream of data mutations for CDC. Redis Pub/Sub is ephemeral and does not retain history, so it cannot serve as a native change data capture source.

• ✓

  Azure SQL Database

  Why this is correct

  Azure SQL Database is the other correct answer, as it has built-in Change Data Capture that leverages the SQL Server transaction log and SQL Agent jobs to asynchronously capture INSERT, UPDATE, and DELETE operations on user tables into dedicated change tables. Standard CDC or net-changes functions in Azure SQL Database allow downstream consumers to query only changed rows with high fidelity, and it is widely used for real-time data warehouse synchronization. This is a mature relational CDC implementation, not a modern application-level feed like Cosmos DB's change feed.

• ✗

  Azure Synapse Link for Azure Cosmos DB

  Why it's wrong here

  Azure Synapse Link for Azure Cosmos DB is an analytical integration feature that continuously copies operational data from a Cosmos DB container into a column-based analytical store for large-scale queries and workloads. Although it internally consumes the Cosmos DB change feed to keep the analytical store in sync, Synapse Link does not expose change data capture as a service to applications — it is not a database engine with its own native CDC. Thus it is a consumer of CDC rather than a provider of a native CDC capability.

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