DVA-C02 Cold Start Practice Question
A developer is troubleshooting an AWS Lambda function that is timing out. The function is configured with a 3-second timeout. Which of the following could cause the function to timeout? (Choose THREE.)
⚠ Common exam trap
Candidates may mistakenly think reserved concurrency of 0 causes a timeout, but it actually causes immediate throttling. The real trap is that cold starts and large deployment packages can both contribute to timeouts, especially when the timeout is short.
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
✓
The function is configured to access a VPC without a NAT gateway.
Lambda timeouts occur when the function execution exceeds the configured timeout. Option A is incorrect because setting reserved concurrency to 0 causes immediate throttling (TooManyRequestsException), not a timeout. Option B is incorrect because a dead-letter queue is for asynchronous invocation failures, not timeouts. Option C is correct: if the function is in a VPC without a NAT gateway, it cannot access external networks, leading to network timeouts. Option D is correct: cold starts can delay execution due to initialization, potentially exceeding the timeout. Option E is correct: a deployment package larger than 50 MB can increase cold start time significantly, causing the function to timeout.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The function's reserved concurrency is set to 0.
Why it's wrong here
Setting a Lambda function's reserved concurrency to 0 explicitly prevents any new invocations from starting. Instead of timing out during execution, any attempt to invoke the function will immediately result in a TooManyRequestsException (HTTP 429 error). The function's code is never even loaded or executed, so a timeout, which implies execution began but didn't complete, cannot occur in this scenario.
- ✗
The function has a dead-letter queue configured.
Why it's wrong here
A dead-letter queue (DLQ) is an asynchronous error handling mechanism for Lambda functions, designed to capture events from failed invocations after all retry attempts have been exhausted. Configuring a DLQ does not introduce any latency or processing overhead that would cause the function itself to time out. Its role is purely reactive, receiving events only after an invocation has already failed due to other reasons, such as a timeout or an unhandled exception.
- ✓
The function is configured to access a VPC without a NAT gateway.
Why this is correct
When a Lambda function is configured to access a VPC but lacks a NAT gateway, outbound internet traffic fails. If the function makes external calls (e.g., to DynamoDB or external APIs), these requests will hang until the function times out.
- ✓
The function experiences a cold start.
Why this is correct
A cold start occurs when AWS Lambda provisions a new execution environment for the function, which involves downloading the deployment package, unzipping it, initializing the runtime, and executing any global code outside the handler. This initialization process, especially for larger packages or complex dependencies, can consume significant time. If this setup duration, combined with the actual handler execution, exceeds the function's configured timeout, the invocation will fail with a timeout error.
- ✓
The function's deployment package is larger than 50 MB.
Why this is correct
A deployment package larger than 50 MB increases the time needed for Lambda to download and extract the code during a cold start. This additional delay can push the total execution time over the configured timeout.
Visual reference
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 |
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.