3.5 - Cloud pricing and purchase options
Cloud+ CV0-004 objective 3.5 covers cloud pricing and purchase options, and how to match them to workloads. Spot instances are the cheapest but can be reclaimed by the provider at any time, so they suit fault-tolerant, interruptible batch work. Reserved instances commit to one to three years of usage up front for a large discount, best for a steady workload that runs 24/7 all year. On-demand instances cost the most per hour but have no commitment, making them the safest choice for unpredictable, short bursts a few times a week. You should also know savings plans, sustained-use discounts and the cost trade-offs of each. Expect scenario questions that describe a usage pattern - interruptible and cheap, steady all year, or bursty and unpredictable - and ask which purchase option minimises cost while meeting the reliability the workload needs.
Cheapest but can be reclaimed anytime (interruptible) = spot. Steady 24/7 all year, commit 1-3 years = reserved. Unpredictable short bursts, no commitment = on-demand.
Practice questions
1. Which pricing option is cheapest but can be reclaimed by the provider at any time, suiting interruptible jobs?
- Reserved
- On-demand
- Spot (correct answer)
- Dedicated
Spot instances use spare capacity at a deep discount but can be terminated with little notice - ideal for batch or fault-tolerant work. Reserved trades commitment for savings.
2. Committing to one to three years of usage up front for a large discount best describes which pricing?
- Interruptible spot pricing
- Reserved instances (correct answer)
- Flexible on-demand rate
- Limited free tier
Reserved instances trade a 1-3 year commitment for a large discount over on-demand, ideal for steady baseline load. Spot is cheapest but can be reclaimed anytime.
3. An instance runs 24/7 at steady load all year. Which purchase option lowers cost the most?
- On-demand
- Spot
- Reserved (correct answer)
- Free tier
Steady always-on workloads suit reserved instances, whose 1-3 year commitment yields the biggest sustained discount. Spot is cheaper per hour but can be reclaimed, breaking 24/7 use.
4. A workload runs unpredictably for short bursts a few times a week. The safest cost fit is:
- Reserved instances
- Spot instances
- On-demand instances (correct answer)
- Dedicated hosts
On-demand fits unpredictable, short-lived bursts with no commitment and no interruption risk. Reserved wastes money when idle; spot risks reclamation mid-burst.
5. Deleting unattached volumes and idle IP addresses to stop paying for them is called removing:
- Orphaned resources (correct answer)
- Reserved instances
- Golden images
- Route tables
Orphaned resources are leftover, unattached assets like idle volumes and unused IPs that still incur charges; cleaning them up cuts waste. Reserved instances are deliberate cost commitments.
6. Reporting each department's cloud usage without billing them internally is called:
- Chargeback
- Right-sizing
- Showback (correct answer)
- Tagging
Showback shows each team its cloud consumption and cost for awareness without actually charging them. Chargeback goes further and bills the cost back to the team's budget.