The answer is that the most likely cause is a malformed request payload or headers sent to the external API. This is because the INVALID_ARGUMENT error specifically signals that the API received data it cannot parse, and the intermittent nature points to a data-dependent issue—such as a field containing unexpected characters, an incorrectly serialized JSON object, or a missing required header—rather than a permanent configuration flaw. On the Google Professional Cloud Developer exam, this scenario tests your ability to distinguish between transient runtime errors and systemic failures, often appearing in troubleshooting questions where the API itself is confirmed healthy. A common trap is to blame network latency or authentication tokens, but the error code itself is your clue: INVALID_ARGUMENT is about the content, not the connection. Remember the mnemonic “Payloads and Headers, not Packets or Credentials” to keep your focus on the data being sent.
PCD Building and testing applications Practice Question
This PCD practice question tests your understanding of building and testing applications. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Exhibit
Refer to the exhibit.
```
Function execution started
Function execution took 120 ms, finished with status: 'connection error'
Error: 3 INVALID_ARGUMENT: Request contains an invalid argument
```
A developer created a Cloud Function that makes an HTTP request to an external API. The above error occurs intermittently. The external API is working correctly. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Refer to the exhibit.
```
Function execution started
Function execution took 120 ms, finished with status: 'connection error'
Error: 3 INVALID_ARGUMENT: Request contains an invalid argument
```
A
The request to the external API has incorrect headers or payload
An invalid argument error strongly suggests the request parameters are incorrect.
B
The function is not handling network retries properly
Why wrong: Retries would not cause an 'INVALID_ARGUMENT' error; they would affect timing or availability.
C
The Cloud Function is not deployed in the same region as the API
Why wrong: Region mismatch would cause latency or connectivity issues, not an invalid argument error.
D
The function is timing out due to long response time
Why wrong: A timeout would show a 'deadline exceeded' error, not 'INVALID_ARGUMENT'.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The request to the external API has incorrect headers or payload
The 'INVALID_ARGUMENT' error indicates the request payload or headers are malformed. Intermittent occurrence suggests a data-dependent issue rather than a permanent config problem.
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.
✓
The request to the external API has incorrect headers or payload
Why this is correct
An invalid argument error strongly suggests the request parameters are incorrect.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The function is not handling network retries properly
Why it's wrong here
Retries would not cause an 'INVALID_ARGUMENT' error; they would affect timing or availability.
✗
The Cloud Function is not deployed in the same region as the API
Why it's wrong here
Region mismatch would cause latency or connectivity issues, not an invalid argument error.
✗
The function is timing out due to long response time
Why it's wrong here
A timeout would show a 'deadline exceeded' error, not 'INVALID_ARGUMENT'.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Command / output trap
A timeout would show a 'deadline exceeded' error, not 'INVALID_ARGUMENT'.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Got this wrong? Here's your next step.
Identify which PCD exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Building and testing applications — This question tests Building and testing applications — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The request to the external API has incorrect headers or payload — The 'INVALID_ARGUMENT' error indicates the request payload or headers are malformed. Intermittent occurrence suggests a data-dependent issue rather than a permanent config problem.
What should I do if I get this PCD question wrong?
Identify which PCD exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This PCD practice question is part of Courseiva's free Google Cloud 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 PCD exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.