The answer is to create a custom Compute Engine image that includes the container runtime and pre-pulled container. This directly addresses the MIG scale up delay by eliminating the network pull of the 2 GB custom image container during instance startup, reducing the time from 5-7 minutes to under 2 minutes. The core concept is that pre-pulling the container into the custom image caches the layers locally, so new workers boot with the container ready to run, bypassing the bottleneck of downloading a large image from Container Registry. On the Google Professional Cloud Architect exam, this scenario tests your understanding of instance templates, managed instance groups, and optimizing startup scripts—a common trap is choosing to simply increase the MIG’s target size or use a smaller container, which ignores the root cause of the network delay. Remember the memory tip: “Pre-pull, not re-pull” to avoid scale-up stalls.
Google PCA Design and plan a cloud solution architecture Practice Question
This PCA practice question tests your understanding of design and plan a cloud solution architecture. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 media streaming company is deploying a new video transcoding pipeline on Google Cloud. The pipeline receives raw video files uploaded to Cloud Storage, triggers a Cloud Function that submits transcoding jobs to a Compute Engine worker pool, and stores the transcoded output in another Cloud Storage bucket. The workers are managed by a managed instance group (MIG) running a custom container image. Currently, when there is a spike in uploads, the MIG takes 5-7 minutes to scale up new workers, causing processing delays. The architect needs to reduce the time to add new workers to under 2 minutes. The workers are stateless and the container image is about 2 GB. What should the architect do?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a custom Compute Engine image that includes the container runtime and pre-pulled container
Option D is correct because creating a custom Compute Engine image that includes the container runtime and pre-pulls the 2 GB container image eliminates the need to download the image during scale-up. This reduces the instance startup time from 5-7 minutes to under 2 minutes, as the container is already cached locally on the image, bypassing the network pull delay.
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 Cloud Run instead of Compute Engine to run the transcoding workers
Why it's wrong here
Cloud Run has a request timeout of 60 minutes and is not designed for batch processing.
✗
Increase the minimum number of instances in the MIG to 10
Why it's wrong here
This increases baseline cost and does not reduce the time to add new workers beyond the minimum.
✗
Replace the Compute Engine workers with Cloud Functions to handle the transcoding
Why it's wrong here
Cloud Functions have a maximum timeout of 60 minutes and may not be suitable for long transcoding jobs.
✓
Create a custom Compute Engine image that includes the container runtime and pre-pulled container
Why this is correct
A custom image with the container already pulled reduces boot time as the image does not need to be downloaded.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may assume increasing the minimum instance count (Option B) solves the scaling delay, but it only pre-provisions a fixed number of instances and does not address the startup latency for additional instances beyond that baseline.
Detailed technical explanation
How to think about this question
Managed instance groups use instance templates to define the boot disk and container image. When a new instance is created, the container runtime must pull the image from Container Registry or Artifact Registry, which for a 2 GB image can take several minutes depending on network bandwidth and registry latency. By baking the container image into a custom machine image (using tools like Packer or a startup script that pre-pulls), the instance starts with the container already available, reducing the cold-start time to the time needed to boot the OS and start the container runtime. This approach is commonly used in high-throughput, latency-sensitive batch processing pipelines.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this PCA question in full detail.
Design and plan a cloud solution architecture — This question tests Design and plan a cloud solution architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a custom Compute Engine image that includes the container runtime and pre-pulled container — Option D is correct because creating a custom Compute Engine image that includes the container runtime and pre-pulls the 2 GB container image eliminates the need to download the image during scale-up. This reduces the instance startup time from 5-7 minutes to under 2 minutes, as the container is already cached locally on the image, bypassing the network pull delay.
What should I do if I get this PCA 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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