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Cloud Digital Leader Practice Question: Run a batch processing job every night for 2 hours
A company plans to run a batch processing job every night for 2 hours. They want to minimize costs while ensuring the job completes within a 4-hour window. Which pricing model should they choose?
⚠ Common exam trap
Google Cloud often tests the misconception that sustained use discounts are the best for any long-running workload, but the trap here is that the 2-hour nightly job does not accumulate enough monthly usage to trigger significant sustained use discounts, making preemptible VMs the correct cost-minimizing choice for interruptible batch jobs.
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
✓
Preemptible VM instances
Preemptible VM instances (B) are ideal for fault-tolerant, short-lived batch jobs that can handle interruptions. They offer significantly lower cost than on-demand instances, and because the job runs for only 2 hours within a 4-hour window, it can be restarted if preempted, ensuring completion at minimal expense.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
On-demand pricing
Why it's wrong here
On-demand pricing charges the full list price per VM with no discounts for short-lived workloads, making it the most expensive option for a nightly 2-hour batch job. While it offers unlimited flexibility with no upfront commitment, it provides no cost optimization for a predictable, recurring, and fault-tolerant workload. Given that the job can tolerate interruptions, preemptible VMs would yield significantly lower costs.
- ✓
Preemptible VM instances
Why this is correct
Preemptible VM instances cost 60–80% less than equivalent on-demand pricing, making them the most economical choice for fault-tolerant batch workloads. Compute Engine can terminate these instances at any time (up to 24 hours after start), so the nightly batch job must be designed to resume or restart gracefully. Since the job runs nightly and can likely be reattempted, preemptible instances are the ideal cost-saving option.
- ✗
Committed use discounts
Why it's wrong here
Committed use discounts require a 1-year or 3-year commitment to a specific amount of vCPUs, memory, and other resources, meaning you pay for capacity even when it is idle. For a job that runs only 2 hours each night, you would be paying for resources that sit unused for the remaining 22 hours of the day, making this option wasteful and not cost-effective. Although the per-hour cost is reduced, the overall financial commitment far exceeds the benefit for such a short and intermittent workload.
- ✗
Sustained use discounts
Why it's wrong here
Sustained use discounts are automatically applied when workloads run for more than 25% of a billing month, but a 2-hour nightly job runs only about 8.3% of the time, so it will not reach the meaningful discount tiers. Even if it did, sustained use only discounts the on-demand base rate, which is still higher than preemptible pricing. Thus, sustained use provides far less savings for this scenario than simply using preemptible VM instances.
Go deeper
Related to this question
Learn chapter
Cloud vs On-Premises Total Cost Analysis
Key term
Batch
Batch is a cloud computing service that runs large numbers of computing jobs as a group, or batch, without needing to manage individual servers.
Key term
Preemptible VM
A preemptible VM is a short-lived, low-cost virtual machine instance that cloud providers can terminate at any time, repurposing the underlying hardware for other tasks.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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