AWS Certified Cloud Practitioner (CLF-C02)Billing, Pricing, and SupportMedium
A media company's AWS bill shows usage measured in GB-months for S3 storage and an EC2 On-Demand rate billed per second (with a 60-second minimum) for Linux instances. A billing analyst is asked to explain why the EC2 cost calculation multiplies the hourly rate by the exact number of seconds the instance ran divided by 3600, rather than rounding up to the nearest hour. What AWS pricing characteristic explains this?
- AAll EC2 instances, regardless of OS, are always billed in fixed hourly increments
- BS3 storage billing determines the EC2 billing granularity
- CEC2 On-Demand Linux instances are billed per-second with a 60-second minimum charge per instance-launch
- DPer-second billing only applies to Reserved Instances, not On-Demand
Show answer & explanationAnswer & explanation
Correct answer: C. EC2 On-Demand Linux instances are billed per-second with a 60-second minimum charge per instance-launch
AWS bills On-Demand and Reserved EC2 instances running Linux (and some other OSes) on a per-second basis, with a minimum charge of 60 seconds per instance run, rather than rounding to the nearest hour, which lowers costs for short-lived workloads.
Why the other options are wrong
- A. Windows and some marketplace AMIs are billed hourly, not all instances, so this is inaccurate.
- B. S3's GB-month billing is unrelated to and does not determine EC2's billing granularity.
- D. Per-second billing applies broadly to On-Demand, Reserved, and Spot Linux instances, not exclusively RIs.
EC2 Per-Second Billing
AWS bills EC2 On-Demand, Reserved, and Spot Linux instances by the second with a 60-second minimum charge, rather than rounding to the nearest full hour.
- Applies to Linux/Unix instances; Windows and some marketplace AMIs remain hourly.
- Minimum billable duration is 60 seconds per instance run.
- EBS volumes are billed per GB-month regardless of EC2 billing granularity.
Memory trick: Linux ticks by the second, Windows still counts by the hour.