DP-900 Describe core data concepts Practice Question
Your company uses Azure SQL Database and needs to ensure that transactions are durable even if the database instance fails. Which feature should you enable?
⚠ Common exam trap
Many exam-takers confuse durability (ensuring committed data survives failures) with high availability or disaster recovery features like geo-replication or failover groups, which address availability rather than the storage-level persistence of transactions.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Zone-redundant storage
Zone-redundant storage (ZRS) replicates your Azure SQL Database transaction logs and data files synchronously across three Azure availability zones within the same region. This ensures that even if an entire zone fails, committed transactions are preserved and the database remains available, providing durability at the storage layer without requiring a separate database replica.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Active geo-replication
Why it's wrong here
Active geo-replication asynchronously copies committed transactions from the primary database to a secondary database in a different Azure region. It is intended for disaster recovery and read-scale out, not for the durability of a single committed transaction on the primary. Because the replication is asynchronous, the secondary can lag behind the primary, meaning an instance failure on the primary could result in the loss of recent transactions that had not yet been copied to the secondary.
- ✓
Zone-redundant storage
Why this is correct
Zone-redundant storage for Azure SQL Database ensures high availability and durability by synchronously replicating data across three Azure availability zones within a region. This architecture guarantees that transactions are durable and data remains accessible even if a single database instance or an entire availability zone fails. The data is protected against zonal outages, satisfying the requirement for durable transactions despite instance failure.
- ✗
Transparent Data Encryption
Why it's wrong here
Transparent Data Encryption (TDE) performs real-time encryption and decryption of data and backup files at rest, protecting against unauthorized access to physical media or stolen backups. It does not alter the transaction commit protocol or the storage redundancy that determines whether a committed transaction survives an instance crash. Durability is guaranteed by the database engine's write-ahead logging process and the underlying storage's synchronous replication, not by encryption.
- ✗
Auto-failover groups
Why it's wrong here
Auto-failover groups provide automatic, policy-based failover to a readable secondary database in another region, ensuring business continuity during an outage. However, under normal operation the failover to the secondary is asynchronous, so the secondary may not contain exactly the same committed transactions as the primary at the moment of failure. The durable commitment of a transaction occurs on the primary's synchronous storage, independent of the failover group's orchestration, meaning this feature does not itself provide transaction durability.
Go deeper
Related to this question
Learn chapter
Data Roles and Core Concepts
Key term
Data
Data is raw, unprocessed information, like numbers, words, or measurements, that can be stored, processed, and analyzed by computers.
Key term
Azure SQL Database
Azure SQL Database is a fully managed relational database-as-a-service (DBaaS) in Microsoft Azure, based on the SQL Server engine, that handles scaling, backups, patching, and high availability automatically.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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