The correct solution is to create a global secondary index (GSI) with enough read capacity for the reporting job and have it query the index instead of scanning the table. This works because DynamoDB shares read capacity between a table and its GSIs by default, so when the reporting job’s scans spike at the top of the hour, the GSI can consume the table’s allocated RCU and cause ProvisionedThroughputExceededException errors even if the table itself has sufficient capacity. By provisioning dedicated RCU on a GSI, you isolate the reporting workload from the main table, preventing throttling without affecting the steady write traffic from the EC2 application. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of how DynamoDB’s capacity allocation works with secondary indexes—a common trap is assuming that increasing table RCU alone fixes GSI throttling, or confusing DynamoDB’s read replicas with RDS features. Remember the memory tip: “GSI gets its own slice—if reads spike, give the index its own RCU price.”
DEA-C01 Data Store Management Practice Question
This DEA-C01 practice question tests your understanding of data store management. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company runs a streaming application on Amazon EC2 instances that writes data to an Amazon DynamoDB table (us-east-1). The data is later consumed by a reporting job that runs every hour. Recently, the reporting job has been failing with ProvisionedThroughputExceededException errors during peak hours. The DynamoDB table uses provisioned capacity with 1000 read capacity units (RCU) and 500 write capacity units (WCU). The reporting job performs scans and reads using eventually consistent reads. The application's write traffic is steady, but the reporting job's reads spike at the top of the hour. The data engineer needs to resolve the throughput exceptions without affecting the application's writes. Which solution should the data engineer implement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a global secondary index (GSI) with enough RCU for the reporting job and have the job query the index instead of scanning the table.
By default, DynamoDB allocates read capacity equally between the table and its global secondary indexes (GSIs). If the table has a GSI, the reporting job's read requests may be throttled due to the GSI's capacity. Adding a GSI with provisioned read capacity dedicated for the reporting job would offload the reads from the main table. Option D is correct. Option A: increasing RCU on the table may not help if the GSI is throttled. Option B: switching to on-demand eliminates throttling but may increase costs and does not guarantee performance. Option C: adding a read replica is not a feature for DynamoDB (only for RDS).
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Create a global secondary index (GSI) with enough RCU for the reporting job and have the job query the index instead of scanning the table.
Why this is correct
Using a GSI with dedicated capacity can isolate the reporting workload and avoid throttling.
Related concept
Static NAT maps one inside address to one outside address.
✗
Increase the table's RCU to 2000.
Why it's wrong here
The issue may be with GSI capacity; increasing table RCU may not help if GSI is throttled.
✗
Create a read replica of the DynamoDB table in a different region.
Why it's wrong here
DynamoDB does not support read replicas; Global Tables replicate both reads and writes.
✗
Switch the table to on-demand capacity mode.
Why it's wrong here
On-demand eliminates throttling but may be more expensive and doesn't address the GSI issue.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DEA-C01 NAT questions on configuration and troubleshooting.
Data Store Management — This question tests Data Store Management — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Create a global secondary index (GSI) with enough RCU for the reporting job and have the job query the index instead of scanning the table. — By default, DynamoDB allocates read capacity equally between the table and its global secondary indexes (GSIs). If the table has a GSI, the reporting job's read requests may be throttled due to the GSI's capacity. Adding a GSI with provisioned read capacity dedicated for the reporting job would offload the reads from the main table. Option D is correct. Option A: increasing RCU on the table may not help if the GSI is throttled. Option B: switching to on-demand eliminates throttling but may increase costs and does not guarantee performance. Option C: adding a read replica is not a feature for DynamoDB (only for RDS).
What should I do if I get this DEA-C01 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DEA-C01 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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