DynamoDB Hot Partition Throttling
A large e-commerce company uses Amazon DynamoDB to store shopping cart data. The table has a partition key of 'user_id' and a sort key of 'item_id'. The application performs frequent updates to the 'quantity' attribute for items in a user's cart. Recently, the operations team noticed that write requests are being throttled during peak shopping hours. The table is provisioned with 10,000 write capacity units (WCUs) and uses DynamoDB Accelerator (DAX) for read caching. The data engineer suspects that the throttling is due to hot partitions. The application uses a single AWS SDK client configured with retries. After reviewing the Amazon CloudWatch metrics, the engineer sees that the WriteThrottleEvents metric spikes for a few partition keys. The table has a high number of partitions. What should the data engineer do to resolve the throttling issue with minimal application changes?
Quick Answer
The answer is to configure DynamoDB Auto Scaling with a maximum WCU setting of 20,000 and a target utilization of 70%. This resolves hot partition throttling by allowing the table to automatically increase its provisioned write capacity during peak traffic, distributing the load more evenly across partitions without requiring any application code changes. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding that DynamoDB hot partition throttling occurs when a single partition key receives disproportionate traffic, and that Auto Scaling is the correct operational fix when the table already has many partitions—manually increasing WCUs or using DAX (which only caches reads) will not solve write-side skew. A common trap is assuming Global Tables or manual capacity adjustments address the root cause, but they do not adapt to variable demand like Auto Scaling does. Memory tip: think “Auto Scale for hot tails”—when one key gets hot, let the table’s capacity auto-adjust to cool it down.
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
✓
Configure DynamoDB Auto Scaling with a maximum WCU setting of 20,000 and a target utilization of 70%.
DynamoDB Auto Scaling can dynamically adjust write capacity in response to traffic patterns, reducing throttling on hot partitions without requiring application changes. Option A is incorrect because permanently increasing WCUs does not adapt to variable demand and may lead to over-provisioning. Option B (Global Tables) replicates data across regions but does not increase write capacity for a single table, so it does not resolve hot partition throttling. Option C (DAX) is a read cache and does not offload write traffic; it only improves read performance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Increase the provisioned write capacity to 20,000 WCUs permanently.
Why it's wrong here
This may eliminate throttling but increases cost and does not adapt to variable traffic.
- ✗
Enable DynamoDB Global Tables to distribute writes across regions.
Why it's wrong here
Global Tables replicate data asynchronously and do not increase write capacity per table.
- ✗
Add more nodes to the DAX cluster to offload write traffic.
Why it's wrong here
DAX is a read cache and does not handle write requests.
- ✓
Configure DynamoDB Auto Scaling with a maximum WCU setting of 20,000 and a target utilization of 70%.
Why this is correct
Auto Scaling dynamically adjusts capacity based on traffic, reducing throttling without permanent overprovisioning.
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Same concept, more angles
1 more way this is tested on DEA-C01
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. An e-commerce company uses Amazon DynamoDB as the primary data store for its product catalog. The table has a simple primary key (ProductID) and handles 10,000 writes per second during peak hours. Recently, the engineering team noticed increased write latency and throttled requests during peak times. The table's provisioned write capacity is set to 12,000 WCU. What is the most likely cause of the throttling?
medium- A.The table has reached the maximum number of partitions
- B.DynamoDB Accelerator (DAX) is not configured
- ✓ C.Write traffic is unevenly distributed across partitions
- D.A global secondary index is consuming write capacity
Why C: DynamoDB partitions data by the primary key's hash value. If write traffic is unevenly distributed across partitions (e.g., a few ProductIDs receive most writes), those hot partitions can exceed their individual throughput limits (3,000 WCU per partition for provisioned tables), causing throttling even when the table's total provisioned WCU of 12,000 is not fully utilized.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DEA-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DEA-C01 exam.