The answer is that three common causes of App Engine deployment failures are an invalid runtime version, an oversized deployment file, and a misconfigured configuration file like cron.yaml. This is because App Engine enforces strict validation at deployment time: the runtime specified in app.yaml must be available in your target region, the total file size must not exceed the 32 MB limit for manual uploads, and any YAML syntax error in files such as cron.yaml or dispatch.yaml will cause the entire deployment to reject. On the Google Professional Cloud Developer exam, this question tests your ability to troubleshoot deployment errors by reading the error message—a common trap is assuming a network issue when the real problem is a deprecated runtime or a missing colon in a YAML file. To remember these three, think of the mnemonic “RFS” for Runtime, File size, and Syntax in config files.
PCD Deploying applications Practice Question
This PCD practice question tests your understanding of deploying 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.
Which THREE common issues cause deployment failures on App Engine? (Choose 3.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Using a runtime version that is not available in the app's region.
Option A is correct because App Engine requires that the runtime version specified in your app.yaml is available in the region where the application is deployed. If you select a runtime version that has been deprecated or is not yet rolled out to that region, the deployment will fail with an error indicating the runtime is unavailable. This is a common issue when using newer runtime versions that are only available in certain regions.
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.
✓
Using a runtime version that is not available in the app's region.
Why this is correct
Some runtimes may not be available everywhere.
Related concept
Read the scenario before looking for a memorised answer.
✓
Exceeding the maximum file size limit for application files.
Why this is correct
There is a 32 MB limit per file.
Related concept
Read the scenario before looking for a memorised answer.
✗
Setting the app to scale to 0 instances.
Why it's wrong here
App Engine Standard does not support scaling to 0.
✓
Uploading a configuration file (e.g., cron.yaml) with invalid syntax.
Why this is correct
Invalid YAML causes deployment failure.
Related concept
Read the scenario before looking for a memorised answer.
✗
Creating a resource with backend type set to 'backend' instead of 'frontend'.
Why it's wrong here
App Engine does not use backend resource types.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that scaling to 0 instances is a valid App Engine configuration, but in reality, the standard environment requires at least one instance to serve traffic, and the flexible environment also has a minimum of 1 instance by default.
Detailed technical explanation
How to think about this question
Under the hood, App Engine uses a regional deployment model where each region has its own set of supported runtime versions and dependencies. When you deploy, the App Engine service checks the runtime version against the region's available list, which is maintained in a regional manifest. A real-world scenario is when a developer uses a runtime version like 'python312' that is only available in 'us-central1' but deploys to 'europe-west1', causing a failure. Additionally, the maximum file size limit (32 MB for the standard environment) is enforced at upload time, and invalid YAML syntax in configuration files like cron.yaml will cause the deployment to reject the file entirely.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Deploying applications — This question tests Deploying applications — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Using a runtime version that is not available in the app's region. — Option A is correct because App Engine requires that the runtime version specified in your app.yaml is available in the region where the application is deployed. If you select a runtime version that has been deprecated or is not yet rolled out to that region, the deployment will fail with an error indicating the runtime is unavailable. This is a common issue when using newer runtime versions that are only available in certain regions.
What should I do if I get this PCD 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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Question Discussion
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