- A
Enable API caching on the stage with a TTL of 300 seconds and configure the client ID as a cache key parameter.
Incorrect: HTTP APIs do not support API Gateway caching. While caching works for REST APIs, it is not available for HTTP APIs.
- B
Enable request validation to reject duplicate requests.
Why wrong: Incorrect: Request validation only validates the request format against a model; it does not detect duplicate payloads or return cached responses.
- C
Configure a usage plan with a throttle rate to limit requests from each client.
Why wrong: Incorrect: A usage plan with throttling limits the request rate per client, but it does not return a previously calculated response; instead, it rejects excess requests with a 429 error.
- D
Enable stage variables to store the previous response.
Why wrong: Incorrect: Stage variables are configuration variables that do not store previous responses.
API Gateway Caching for Duplicate Request Deduplication
This DVA-C02 practice question tests your understanding of development with aws services. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. A key principle to apply: aPI Gateway HTTP API. 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 developer is building a RESTful API using Amazon API Gateway (HTTP API) and AWS Lambda. The API receives a large number of requests with duplicate payloads within a short time window. To improve performance and reduce costs, the developer wants to ensure that if the same request (based on a unique client ID) is sent within 5 minutes, the Lambda function is not invoked again, and the previously calculated response is returned. Which API Gateway feature should the developer use?
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
Enable API caching on the stage with a TTL of 300 seconds and configure the client ID as a cache key parameter.
Amazon API Gateway HTTP APIs do not support caching. Therefore, none of the provided options correctly achieve the goal of returning a previously calculated response without invoking the Lambda function. The developer would need to implement caching at the Lambda layer using an external cache like Amazon ElastiCache or DynamoDB.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Enable API caching on the stage with a TTL of 300 seconds and configure the client ID as a cache key parameter.
- ✗
Enable request validation to reject duplicate requests.
Why it's wrong here
Incorrect: Request validation only validates the request format against a model; it does not detect duplicate payloads or return cached responses.
- ✗
Configure a usage plan with a throttle rate to limit requests from each client.
Why it's wrong here
Incorrect: A usage plan with throttling limits the request rate per client, but it does not return a previously calculated response; instead, it rejects excess requests with a 429 error.
- ✗
Enable stage variables to store the previous response.
Why it's wrong here
Incorrect: Stage variables are configuration variables that do not store previous responses.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Candidates often assume that API Gateway caching works for all API types, but HTTP APIs do not have caching capability. This leads to incorrectly selecting Option A.
Detailed technical explanation
How to think about this question
API Gateway caching works by generating a cache key from the configured parameters (e.g., client ID) and the request path. When a cache hit occurs, the response is served directly from the cache without reaching the backend. The TTL value (in seconds) controls how long the cached response is considered fresh; after expiry, the next request triggers a new Lambda invocation. In a real-world scenario, this is ideal for idempotent APIs where repeated identical requests should return the same result, such as payment confirmation lookups or order status checks.
KKey Concepts to Remember
- API Gateway HTTP API
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
API Gateway HTTP API
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.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
What to study next
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FAQ
Questions learners often ask
What does this DVA-C02 question test?
Development with AWS Services — This question tests Development with AWS Services — API Gateway HTTP API.
What is the correct answer to this question?
The correct answer is: Enable API caching on the stage with a TTL of 300 seconds and configure the client ID as a cache key parameter. — Amazon API Gateway HTTP APIs do not support caching. Therefore, none of the provided options correctly achieve the goal of returning a previously calculated response without invoking the Lambda function. The developer would need to implement caching at the Lambda layer using an external cache like Amazon ElastiCache or DynamoDB.
What should I do if I get this DVA-C02 question wrong?
Review aPI Gateway HTTP API, then practise related DVA-C02 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
API Gateway HTTP API
About these practice questions
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Same concept, more angles
1 more ways this is tested on DVA-C02
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. A developer is building a RESTful API using Amazon API Gateway. The API experiences high traffic spikes, and many requests are for the same data (e.g., a product catalog). The developer wants to reduce the load on the backend Lambda functions and improve response times for repeated requests. Which feature should the developer enable?
easy- ✓ A.Enable API Gateway caching and set a TTL.
- B.Use CloudFront with the API Gateway as an origin.
- C.Enable throttling on the API Gateway usage plan.
- D.Use a DynamoDB Accelerator (DAX) cluster for the backend database.
Why A: API Gateway caching stores responses from backend Lambda functions for a configurable time-to-live (TTL). When a request for the same data (e.g., a product catalog) arrives within the TTL period, API Gateway serves the cached response directly, reducing the number of invocations to the Lambda function and improving response latency. This directly addresses the need to reduce load on the backend and improve response times for repeated requests.
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Last reviewed: Jun 11, 2026
This DVA-C02 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 DVA-C02 exam.
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