Committed use discounts

This page describes how committed use discounts (CUDs) work with AlloyDB for PostgreSQL.

Overview of committed use discounts

Committed use discounts (CUDs) for AlloyDB provide deeply discounted prices in exchange for your commitment to continuously use database instances for a one-year or three-year term.

AlloyDB CUDs are ideal for workloads with predictable resource needs. You commit to a consistent amount of usage, measured in cost per hour of equivalent on-demand spending, for a one-year or three-year term. In exchange, you receive a discounted rate for AlloyDB on the applicable usage your commitment covers.

You can purchase CUDs from any Cloud Billing account, and the discount applies to any eligible usage in projects that the Cloud Billing account pays for. When you purchase a AlloyDB CUD, you pay the same commitment fee for the entirety of the commitment term, even if the price of applicable usage changes. You still receive the same discount percentage on applicable usage in the event of a price change. The commitment fee is billed monthly.

For more information about your bill, see Analyze the effectiveness of your spend-based committed use discounts.

Usage that qualifies for AlloyDB CUDs

CUDs automatically apply to aggregate AlloyDB instance usage across all regions and all projects, giving you low, predictable costs, without the need to make any manual changes or updates yourself. This flexibility helps you achieve high utilization rates across your commitments, saving you time and money.

AlloyDB CUDs apply to all AlloyDB database instance vCPUs and memory usage. AlloyDB CUDs do not apply to storage, backups, and network data transfer.


AlloyDB CUDs give you a 25% discount off on-demand pricing for a one-year commitment and a 52% discount off on-demand pricing for a three-year commitment. This discount significantly reduces your AlloyDB costs.

Purchase AlloyDB CUDs

You can purchase a AlloyDB CUD in the Google Cloud console billing page. Select the Commitments tab, then select the PURCHASE action at the top. After purchasing a CUD, the commitment is effective starting within the next hour of purchase.

Before you purchase a CUD, read the Service Specific Terms regarding committed units.

To learn more, including how to purchase spend-based commitments, see Committed use discounts.

Example use case

This example shows you how to calculate your discount and costs for an high-availability (HA) instance.

Key points to remember:

  • AlloyDB CUDs apply only to vCPUs and memory.
  • AlloyDB CUDs do not apply to storage, backups, or network data transfer.
  • AlloyDB CUDs apply to all instances.
  • AlloyDB CUDs are measured in dollars per hourly on-demand commitment.

How to calculate an hourly on-demand commitment

Your commitment should represent your expected minimum hourly expenditure on AlloyDB capacity across your projects over the next one or three years.

As an example, consider an AlloyDB HA primary instance, which has a leader and a standby node in the us-central1 region. This instance has 16 vCPUs and 128 GB RAM.

From the pricing page, you can calculate the approximate hourly commitment cost as follows:

  • Combined expenditure in us-central1 for the leader and standby nodes: 2 * ((16 vCPU * $0.06608 per vCPU per hour) + (128 GB * $0.0112 per GB per hour)) = $4.98 per hour

If you expect to spend that minimum of $4.98 per hour continuously for the next year or more, then you can make a commitment for that amount. In other words, when purchasing that CUD, you would enter "$4.98" as the hourly on-demand commitment amount.

If, on the other hand, you expect to scale down the capacity occasionally, you can make a commitment for a lower amount. Any expenditure above that limit is charged at the on-demand rate.

Continuing this example, assume that you do decide on a commitment of $4.98 per hour. As your next step, you choose the length of the commitment's period.

As a basis for comparison, compute the on-demand cost of AlloyDB capacity at the chosen commitment rate, without the application of any commitment discounts:

  • Monthly cost based on on-demand pricing: $4.98 per hour * 730 hours = $3,635.40 per month

From here, you can calculate the monthly costs and savings you would see under a 1-year CUD, applying its 25% discount, compared to a year of paying the full on-demand rates:

  • Monthly cost of a 1-year, $4.98/hour commitment: ($4.98 per hour - 25% discount) * 730 hours = $2,726.55 per month
  • Total savings per month: $3,635.40 - $2,726.55 = $908.85
  • Total savings with a 1-year, $4.98/hour commitment: $908.85 per month * 12 months = $10,906.20

You can apply similar math to calculating the costs and savings of a 3-year CUD, with its 52% discount compared to on-demand rates:

  • Monthly cost of a 3-year, $4.98/hour commitment: ($4.98 per hour - 52% discount) * 730 hours = $1,744.99 per month
  • Total savings per month: $3,635.40 - $1,744.99 = $1,890.40
  • Total savings with a 3-year, $4.98/hour commitment: $1,890.40 per month * 36 months = $68,054.68

As you can see, a commitment that covers your expected minimum AlloyDB usage over the years to come can lead to significant savings. Read on for our recommendations on choosing the right CUD size for your AlloyDB projects.

Recommendations for choosing a commitment

When making the decision on whether to purchase CUDs, consider the following:

  • Regions: AlloyDB CUDs apply across regions. If you have AlloyDB instances in multiple regions, calculate the expenditure across all the regions while making a commitment.
  • Projects: Determine the consistent baseline vCPU/RAM usage per project. Consider that production loads usually run 100% of the time, while development or staging environments are usually run more intermittently.
  • Instances: AlloyDB instances are usually run 24/7, so it's common to buy CUDs for 100% consumption. If you have instances that are run only for bursts or shorter durations, exclude them from your calculations, and pay on-demand rates for those instances.

What's next

Learn how to purchase spend-based commitments in Committed use discounts.