Did you know that adjusting machine types can automatically save a lot of money? This mecanism is called sustained use discounts.
When you run an instance for an entire month, you don’t pay the full price. Discount rates are different between predefined and custom machine types. For a predefined machine type, each 25% is charged with a different discount rate:
- First quarter is fully charged
- Second quarter costs 20% less
- Third quarter costs 40% less
- Last quarter costs 60% less
This is automatic and you don’t have to ask or enable an option!
But what if your workload doesn’t run for an entire month? Don’t worry, GCP offer you a way to benefit from a discount too. This is called inferred instances and allow you to combine your usage based on duration.
For example, imagine we need 4 instances for only a quarter of the month. GCP can aggregate usage and apply discount equivalently as a single instance running for the entire month.
Two conditions are required to create inferred instances :
- Only instances of the same machine type can combine,
- Only instances in the same zone are counted.
Learn more about discounts
The Google Compute Engine documentation covers the details about the sustained use discounts.