- A
Use a Task state with .waitForTaskToken and have the Lambda function return the token upon completion.
Allows asynchronous execution with callback.
- B
Use a Task state that directly invokes the Lambda function synchronously.
Why wrong: Synchronous invocation times out with the function.
- C
Use a Parallel state to run multiple Lambda functions concurrently.
Why wrong: Does not solve timeout issue.
- D
Use a Choice state to branch based on the Lambda function's output.
Why wrong: No relation to asynchronous execution.
Question 937 of 1,616
Using .waitForTaskToken in Step Functions for Asynchronous Lambda Completion
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. 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 developer is designing a workflow using AWS Step Functions that includes a task to invoke an AWS Lambda function. The Lambda function sometimes times out due to long-running operations. The developer needs the workflow to wait for the Lambda function to complete asynchronously and retry on failure. Which Step Functions pattern 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
✓
Use a Task state with .waitForTaskToken and have the Lambda function return the token upon completion.
Option A is correct because the `.waitForTaskToken` pattern in a Task state allows the Step Functions workflow to pause and wait for an external process (like a long-running Lambda function) to complete asynchronously. The Lambda function receives a task token and must call `SendTaskSuccess` or `SendTaskFailure` with that token when it finishes, enabling the workflow to handle timeouts and retries reliably without hitting the 15-minute Lambda execution limit.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Use a Task state with .waitForTaskToken and have the Lambda function return the token upon completion.
Why this is correct
Allows asynchronous execution with callback.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use a Task state that directly invokes the Lambda function synchronously.
Why it's wrong here
Synchronous invocation times out with the function.
- ✗
Use a Parallel state to run multiple Lambda functions concurrently.
Why it's wrong here
Does not solve timeout issue.
- ✗
Use a Choice state to branch based on the Lambda function's output.
Why it's wrong here
No relation to asynchronous execution.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume synchronous invocation (Option B) is sufficient, but they overlook the fact that Step Functions cannot natively wait for a Lambda function that times out or runs longer than the Lambda timeout, whereas `.waitForTaskToken` provides the necessary asynchronous callback mechanism.
Detailed technical explanation
How to think about this question
The `.waitForTaskToken` pattern works by embedding a unique token in the task input (via the `TaskToken` field) that the Lambda function must return via the AWS SDK `SendTaskSuccess` or `SendTaskFailure` API calls. This decouples the workflow from the Lambda execution duration, allowing the function to run beyond the Step Functions 1-year timeout limit and enabling robust retry policies with exponential backoff. In real-world scenarios, this is critical for tasks like processing large files or calling external APIs that may take minutes or hours.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
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
Got this wrong? Here's your next step.
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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 — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a Task state with .waitForTaskToken and have the Lambda function return the token upon completion. — Option A is correct because the `.waitForTaskToken` pattern in a Task state allows the Step Functions workflow to pause and wait for an external process (like a long-running Lambda function) to complete asynchronously. The Lambda function receives a task token and must call `SendTaskSuccess` or `SendTaskFailure` with that token when it finishes, enabling the workflow to handle timeouts and retries reliably without hitting the 15-minute Lambda execution limit.
What should I do if I get this DVA-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 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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