Which EC2 purchasing option fits steady, predictable 1-year traffic?

CLF-C02 By islever Editorial Last updated

Compare AWS pricing models. Identify AWS compute services.

Short answer

B Reserved Instances give a deep discount over On-Demand for steady, predictable EC2 workloads committed for one year with no interruption.

Question

An online gaming company needs to choose a purchasing option to run its Amazon EC2 instances for 1 year. The web traffic is consistent, and any increases in traffic are predictable. The EC2 instances must be online and available without any disruption.
Which EC2 instance purchasing option will meet these requirements MOST cost-effectively?
  1. On-Demand Instances
  2. Reserved Instances Correct Answer
  3. Spot Instances
  4. Spot Fleet

Key Takeaways

The test is separating "predictable, must-not-be-interrupted, fixed 1-year term" from interruptible bargain hunting — the trap is picking Spot because it is cheapest on paper.

This question tests how to match an Amazon EC2 purchasing option to a steady, predictable workload that must stay online for one year. Reserved Instances are the most cost-effective choice because the one-year commitment earns a large discount without any interruption risk.

Common mistake: The most common wrong answer is Spot Instances (or a Spot Fleet) because they carry the deepest discount, but Spot capacity can be reclaimed with a two-minute warning, which violates the requirement that the gaming servers stay online without disruption.

Expert Analysis

Why the Answer Is Correct

Reserved Instances are the right fit because every constraint in the scenario points to them: the web traffic is consistent, any spikes are predictable, and the company already knows it needs the EC2 capacity for one year. Committing to a one-year term converts that certainty into a significant discount versus On-Demand pricing, while the instances remain dedicated to the account and are never interrupted. As Anyio noted, RIs offer "a significant discount (up to 72%) compared to On-Demand pricing" and can also provide a capacity reservation in a specific Availability Zone. Nothing in the requirements demands the flexibility of Savings Plans beyond the instance family, and no interruption is acceptable, so the reservation model is the most cost-effective safe option.

Why the Other Options Are Wrong

On-Demand Instances preserve flexibility but are the most expensive way to run a workload the company already knows it will keep for twelve months, so they fail the "MOST cost-effectively" test. Spot Instances and Spot Fleet offer the largest discounts, but Spot capacity is spare Amazon EC2 capacity that can be reclaimed at short notice — unacceptable for a live game backend that must stay online without disruption. A Spot Fleet is simply a collection of Spot and optionally On-Demand instances, so it inherits the same interruption exposure. As lunamuller summarized, the deciding clues are "instance for 1 year", "traffic is predictable" and "available without any disruption".

Community Comment Notes

Consensus among commenters is strongly behind Reserved Instances, with Sir_Kay emphasizing that committing to a one-year term can save "up to 75% compared to On-Demand pricing" for predictable traffic, and parrtner73 reducing the logic to "predictable, long term". Ruffyit, TheFivePips and Buda all walk through the same elimination: On-Demand is pay-as-you-go and less cost-effective for consistent workloads, while RIs are suited to consistent, predictable demand. Abhi_2005 raised a side point about Savings Plans versus RIs and their term constraints, which does not change the answer here because Reserved Instances are the option offered that best matches a fixed one-year, non-interruptible commitment.

Official Reference

These links open the official vendor documentation in a new tab.

Exam Strategy

Scan the stem for three signals: a fixed term (1 year), predictable/steady demand, and a no-disruption requirement. Those three together map to Reserved Instances; reserve Spot for fault-tolerant, interruptible batch work and On-Demand for short-lived or unpredictable workloads.

Frequently Asked Questions

Why are Spot Instances wrong for a gaming backend that must stay online?

Spot capacity is spare EC2 capacity that AWS can reclaim with a short interruption notice, so it cannot guarantee uninterrupted availability for a live game.

Would On-Demand Instances ever be a better fit than Reserved Instances here?

Only if the workload were short-lived or unpredictable. With a known one-year need and steady traffic, On-Demand costs more than a one-year Reserved Instance commitment.

More CLF-C02 FAQ →

Discussion 16 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 16

  1. Sir_Kay 👍 6 Answered B
    Reserved Instances are the most cost-effective purchasing option for workloads with predictable, steady usage patterns (like the online gaming company's consistent and predictable traffic). By committing to a one-year term, the company can save up to 75% compared to On-Demand pricing.
  2. TheFivePips 👍 4 Answered B
    A. On-Demand Instances: Pay-as-you-go without upfront commitment; less cost-effective for consistent workloads. B. Reserved Instances: Reserved Instances (RIs) provide a significant discount (compared to On-Demand Instances) in exchange for a commitment of one or three years. They are suitable for consistent, predictable workloads. RIs offer cost-effectiveness while ensuring the EC2 instances are online and available without disruptions. C. Spot Instances: Bid for unused capacity; cost savings but may not provide consistent availability. D. Spot Fleet: Collection of Spot Instances; offers flexibility but inherits characteristics of Spot Instances.
  3. Ruffyit 👍 4
    A. On-Demand Instances: Pay-as-you-go without upfront commitment; less cost-effective for consistent workloads. B. Reserved Instances: Reserved Instances (RIs) provide a significant discount (compared to On-Demand Instances) in exchange for a commitment of one or three years. They are suitable for consistent, predictable workloads. RIs offer cost-effectiveness while ensuring the EC2 instances are online and available without disruptions. C. Spot Instances: Bid for unused capacity; cost savings but may not provide consistent availability. D. Spot Fleet: Collection of Spot Instances; offers fl
  4. Anyio 👍 4 Answered B
    The Correct answer is B. Amazon EC2 Reserved Instances (RI) provide a significant discount (up to 72%) compared to On-Demand pricing and provide a capacity reservation when used in a specific Availability Zone. Terms (avg. discount off On-Demand) - 1yr (40%), 3yr (60%) https://aws.amazon.com/ec2/pricing/reserved-instances/
  5. anup77777 👍 3
    B. Reserved Instances: Reserved Instances (RIs) provide a significant discount (compared to On-Demand Instances) in exchange for a commitment of one or three years. They are suitable for consistent, predictable workloads. RIs offer cost-effectiveness while ensuring the EC2 instances are online and available without disruptions.
Show 11 more comments
  1. Buda 👍 2 Answered B
    B. Reserved Instances: Reserved Instances (RIs) provide a significant discount (compared to On-Demand Instances) in exchange for a commitment of one or three years. They are suitable for consistent, predictable workloads. RIs offer cost-effectiveness while ensuring the EC2 instances are online and available without disruptions
  2. Abhi_2005 👍 2
    eventhough you have saving plans as a option we have to choose Reserved Instances only because in saving plans we have to choose a fixed time but in RI there is no time limit - If i am wrong please mention the correct reason
  3. lunamuller 👍 2 Answered B
    Answer B is Correct. Key: "instance for 1 year" "traffic is predictable" "available without any disruption"
  4. parrtner73 👍 2 Answered B
    predictable, long term
  5. alanb1978 👍 2 Answered B
    Instâncias Reservadas
  6. Dimagi 👍 1 Answered B
    The company needs EC2 instances for 1 year, with consistent traffic and no interruptions. Reserved Instances are the most cost-effective option because they offer discounted pricing in exchange for a 1-year or 3-year commitment.
  7. bn04 👍 1 Answered B
    You can purchase a Reserved Instance for a one-year or three-year commitment
  8. lio101 👍 1
    if there was saving plans? what can we choose?
  9. Dipa_2910 👍 1 Answered B
    Reserved instances
  10. asdfcdsxdfc 👍 1 Answered B
    B looks correct
  11. fastracecar21 👍 1 Answered B
    B is correct

Reader comments & corrections

No reader corrections yet — spotted an error or have a note? Share it below.

Log in to comment, report an error, or add a note about this question.

Which migration strategies move a cloud-incompatible CMS with least effort?

S-grade

Launching Third-Party IDS in AWS

S-grade

Which AWS Support Plan Offers API Access Most Cost-Effectively?

S-grade

S3 Express One Zone for Single-Digit Millisecond Latency

S-grade

Practice All CLF-C02 Questions

Access 120 questions with complete answers and detailed explanations.

View Full CLF-C02 Practice Test →

← Back to CLF-C02 Study Guide