DOP-C02 Incident and Event Response Practice Question
A DevOps engineer is troubleshooting a Lambda function that times out after 3 seconds. The function makes an HTTP request to an external API. The function's timeout setting is 10 seconds. What is the most likely cause of the timeout?
⚠ Common exam trap
Candidates often assume the Lambda function's configured timeout (10 seconds) is the only timeout that matters, overlooking that application-level timeouts (like HTTP client timeouts) can fire independently and cause earlier failures.
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 HTTP client's timeout is set to a low value.
The Lambda function times out after 3 seconds, which is most likely due to an HTTP client timeout explicitly set to a low value (e.g., 3 seconds) inside the function code. Even though the Lambda function's configured timeout is 10 seconds, the HTTP client's internal timeout fires first, causing the function to fail before the Lambda timeout is reached. This is the most likely cause because the symptom matches a client-side timeout rather than a server-side or infrastructure issue.
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 external API is throttling the request.
Why it's wrong here
An external API responding with 429 Too Many Requests or 502 because of throttling returns a status code quickly; it does not make the HTTP client wait for the full 3-second window. Throttling errors surface as a non-2xx response that your code can handle, not as a timeout exception, so this would not produce the consistent 3-second timeout symptom.
- ✓
The HTTP client's timeout is set to a low value.
Why this is correct
The default inactivity timeout for many HTTP clients is exactly 3 seconds, so when the external API takes longer than that to respond, the client aborts with a timeout error before the Lambda function's own timeout limit is reached. Raising the client timeout (or configuring connection/read timeouts) to exceed the expected API response time directly resolves the issue. This matches the symptom precisely because every call that exceeds the threshold fails at the same 3-second mark.
- ✗
The Lambda function is not in a VPC.
Why it's wrong here
Lambdas outside a VPC are attached to an AWS-managed network that provides direct internet access, so they do not encounter a network-bound 3-second timeout when reaching a public API. VPC placement affects which private resources are reachable and requires a NAT gateway for internet, but the absence of a VPC is the network configuration most likely to avoid timeouts, not cause them.
- ✗
The Lambda function's memory is insufficient.
Why it's wrong here
Memory size controls the CPU proportion and memory available; insufficient memory leads to out-of-memory errors or OOM kills, not socket-level timeout exceptions after a fixed interval. The consistent 3-second timeout indicates something is timing out at the connection layer, whereas memory pressure would cause varied failures or a higher error rate correlated with algorithm complexity. Since the symptom is a duration-based cutoff, the root cause cannot be memory.
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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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DOP-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 DOP-C02 exam.