Answer: Configure DynamoDB in on-demand mode by using the DynamoDB Standard table class.

## Explanation **Correct Answer: B** **Why Option B is correct:** 1. **Unpredictable traffic pattern**: The question states that "application traffic will be unpredictable." DynamoDB On-Demand mode is specifically designed for unpredictable workloads where you cannot accurately forecast capacity requirements. 2. **Moderate to high throughput**: On-Demand mode can handle moderate to high throughput automatically without capacity planning. 3. **Cost-effectiveness**: For unpredictable workloads, On-Demand mode is typically more cost-effective than provisioned capacity because: - You pay only for what you use (per request pricing) - No need to provision capacity in advance - No need to pay for unused provisioned capacity during low-traffic periods - Automatic scaling without any configuration 4. **Standard table class**: This is appropriate for general-purpose workloads with frequent access patterns. **Why other options are incorrect:** **Option A (Provisioned with auto scaling):** - While auto scaling can help with some unpredictability, it still requires setting minimum and maximum capacity limits - You pay for provisioned capacity even during low-traffic periods - Less cost-effective for truly unpredictable workloads compared to On-Demand **Option C (Provisioned with Standard-IA table class):** - DynamoDB Standard-IA is designed for infrequently accessed data with lower storage costs but higher read/write costs - This is inappropriate for a web application with "moderate to high" throughput - The higher per-request costs would make this option expensive for the described workload **Option D (On-Demand with Standard-IA table class):** - Standard-IA table class has higher read/write costs than Standard table class - This would be more expensive than Option B for moderate to high throughput workloads - Standard-IA is optimized for infrequently accessed data, not active web application workloads **Key AWS Concepts:** - **DynamoDB On-Demand**: Pay-per-request pricing model, ideal for unpredictable workloads - **DynamoDB Provisioned**: Pay for provisioned read/write capacity, better for predictable workloads - **DynamoDB Standard Table Class**: Default table class for general-purpose workloads - **DynamoDB Standard-IA Table Class**: Lower storage costs but higher read/write costs, designed for infrequently accessed data For the given scenario with unpredictable traffic and moderate to high throughput, DynamoDB On-Demand with Standard table class provides the most cost-effective solution.

Author: LeetQuiz Editorial Team