Azure Cosmos DB Table API for Dedicated Throughput

AZ-305 By islever Editorial Last updated

Design data storage solutions for relational data

Short answer

A An Azure Cosmos DB database provides dedicated throughput via Request Units (RUs) to ensure fast, consistent read/write performance for Table API data.

Question

You are building an app named App1 that will store structured and unstructured data by using the Azure Table storage REST API.
You need to recommend a solution that meets the following requirements:
• Provides dedicated throughput and the fastest possible read and write times for the data
• Minimizes storage costs
What should you include in the recommendation?
  1. an Azure Cosmos DB database Correct Answer
  2. a standard storage account
  3. a premium storage account
  4. Azure Cache for Redis

Key Takeaways

The question tests knowledge of specialized NoSQL table storage versus general-purpose blob/file storage, with the trap being the assumption that 'Table Storage' implies only the legacy Azure Table Storage service rather than the modern Cosmos DB Table API.

This question evaluates the selection of Azure storage services for structured data requiring dedicated throughput and low latency. Azure Cosmos DB is identified as the correct solution due to its provisioned Request Units (RUs) that guarantee performance while maintaining cost efficiency compared to premium general-purpose accounts.

Common mistake: Candidates often select a standard or premium storage account (Option B or C), mistakenly believing that general-purpose storage provides better throughput or that the specific mention of 'Table storage REST API' refers exclusively to the legacy Azure Table Storage which does not offer dedicated throughput modes.

Expert Analysis

Why the Answer Is Correct

Azure Cosmos DB offers a Table API that is fully compatible with the Azure Table Storage REST API but provides significantly superior performance characteristics. By using a Cosmos DB database, you can enable 'dedicated throughput,' which means the database is provisioned with specific Request Units (RUs). This guarantees single-digit millisecond latencies for reads and writes, satisfying the requirement for the 'fastest possible read and write times.' It also minimizes costs by allowing you to pay only for the capacity you need, rather than reserving expensive premium storage tiers.

Why the Other Options Are Wrong

A standard storage account (Option B) shares resources with other tenants and does not offer dedicated throughput or guaranteed low-latency SLAs for table operations. A premium storage account (Option C) is designed primarily for IOPS-intensive workloads like VM disks (page blobs) and does not support the Table API structure natively in a way that offers dedicated throughput scaling. Azure Cache for Redis (Option D) is an in-memory data store optimized for caching and session state, not for persistent structured data storage via the Table API, and it would incur significantly higher costs for large datasets.

Community Comment Notes

The community consensus strongly supports Option A. As noted by user gpais, "Dedicated Throughput and Speed: Azure Cosmos DB for Table uses provisioned throughput measured in Request Units (RUs) to provide dedicated, guaranteed throughput." This aligns with the core differentiator of Cosmos DB over legacy storage solutions.

Exam Strategy

When a question mentions 'Table Storage' alongside requirements for 'dedicated throughput' or 'millisecond latency', immediately consider Azure Cosmos DB's Table API. Legacy Azure Table Storage does not support dedicated throughput; only Cosmos DB does.

Frequently Asked Questions

Why isn't Azure Cache for Redis used for Table data?

Redis is an in-memory cache, not a persistent table storage solution. It lacks the Table API compatibility and is too expensive for bulk structured data storage.

Does 'Table storage REST API' mean only legacy storage?

No. While legacy Azure Table Storage exists, Cosmos DB's Table API is fully compatible with the same REST endpoints but adds features like dedicated throughput and global distribution.

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Discussion 1 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 1

  1. gpais 👍 1 Answered A
    • Dedicated Throughput and Speed: Azure Cosmos DB for Table uses provisioned throughput measured in Request Units (RUs) to provide dedicated, guaranteed throughput. It delivers guaranteed single-digit millisecond latencies at the 99th percentile for both reads and writes, making it the fastest possible option for table-structured data.

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