AZ-900 Describe Azure architecture and services Practice Question
Which Azure service provides fully managed, distributed in-memory caching for data like session state and frequently accessed database queries?
⚠ Common exam trap
A common mix-up: candidates confuse Azure Cache for Redis with Azure SQL Database In-Memory OLTP, because both involve in-memory data, but In-Memory OLTP is a database engine feature for accelerating OLTP workloads, not a distributed caching service for session state or query results.
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 fully managed, distributed in-memory caching service based on the open-source Redis engine. It is specifically designed to store session state and cache frequently accessed database queries, providing low-latency data access by keeping data in memory rather than on disk.
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 Storage Table
Why it's wrong here
Azure Storage Table is a schemaless NoSQL key-value service that persists data to disk, making it cost-effective for storing large volumes of structured data with millisecond-level latency. It lacks the in-memory caching capabilities of Redis, such as sub-millisecond reads, time-to-live (TTL), and eviction policies. Therefore, while it can store session state, it is not designed for high-speed caching of frequently accessed application data.
- ✓
Azure Cache for Redis
Why this is correct
Azure Cache for Redis is a managed in-memory data store built on the open-source Redis engine, providing sub-millisecond read/write performance for frequently accessed data and session state. It supports rich data structures (strings, hashes, lists), TTL, and pub/sub, making it a distributed cache that can scale across multiple app instances. Its in-memory design and automatic failover options make it the correct choice for low-latency caching scenarios.
- ✗
Azure SQL Database In-Memory OLTP
Why it's wrong here
Azure SQL Database In-Memory OLTP is a performance feature that accelerates online transaction processing by using memory-optimized tables and natively compiled stored procedures within the SQL engine. Unlike Redis, it is not a standalone, independently accessible cache service; it is tightly coupled to the database and designed to improve SQL workload throughput, not to cache arbitrary application objects. Consequently, it cannot serve as a general-purpose distributed cache for session data.
- ✗
Azure CDN edge caching
Why it's wrong here
Azure CDN edge caching is a content delivery network that caches static web content such as images, CSS, and JavaScript on edge servers located around the globe. It operates via HTTP caching rules and is optimized for reducing latency in content distribution, not for caching dynamic application data like database query results or session state. Since it lacks the flexible TTL and eviction controls of an in-memory cache, it is not a substitute for Azure Cache for Redis.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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