AZ-900 Describe Azure architecture and services Practice Question
Which Azure service provides a managed caching layer to reduce database load and improve application response times?
⚠ Common exam trap
It's easy for candidates to confuse a NoSQL database (like Cosmos DB or Table Storage) with a caching service, not realizing that caching services are specifically designed for temporary, in-memory storage to offload persistent databases, not for long-term data persistence.
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
✓
Azure Cache for Redis
Azure Cache for Redis is a managed in-memory caching service based on the open-source Redis engine. It provides a high-throughput, low-latency data store that can temporarily hold frequently accessed data, thereby reducing the number of direct queries to a backend database and improving application response times. This makes it the correct choice for a managed caching layer.
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 Cosmos DB
Why it's wrong here
Azure Cosmos DB is a globally distributed, multi-model database service that stores data durably across regions and provides configurable consistency and millisecond-level read latency. Although it includes some internal caching for index and data access, it is fundamentally a primary data store, not a caching layer. Using Cosmos DB to cache would be redundant and cost-inefficient; the correct caching service is Azure Cache for Redis.
- ✗
Azure SQL Database
Why it's wrong here
Azure SQL Database is a fully managed relational database service that stores normalized, structured data in tables and is optimized for transactional workloads. Its in-memory features, such as columnstore or buffer pool, are internal performance optimizations, not a user-accessible caching layer. To offload read queries and reduce load on the database, you would place Azure Cache for Redis in front, not use SQL Database itself as a cache.
- ✓
Azure Cache for Redis
Why this is correct
Azure Cache for Redis is a managed, in-memory data cache service based on the Redis engine, delivering extremely low latency (sub-millisecond) and high throughput for frequently accessed data. It is purpose-built for caching workloads such as session state, API responses, and database query results, thereby offloading pressure from databases and improving application performance. This service directly matches the requirement for a dedicated caching solution, making it the correct answer.
- ✗
Azure Table Storage
Why it's wrong here
Azure Table Storage is a NoSQL key-value/entity store that persists structured, semi-structured, and schema-less data to disks in Azure Storage. While it offers fast access for significant data volumes, it does not provide managed in-memory caching for sub-millisecond reads. Caching requires a dedicated in-memory service like Azure Cache for Redis; therefore, it is incorrect for the scenario of reducing database load via caching.
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