AzureAzure SQL DatabaseDatabase

`azurerm_mssql_elasticpool` cost estimation

A shared pool of resources for many Azure SQL databases. Priced per pool vCore-hour (or DTU) plus pool storage, amortizing capacity across databases.

An azurerm_mssql_elasticpool lets many Azure SQL databases share a single allocation of compute, instead of each database provisioning its own. It's the right model when you have lots of databases with uneven, non-overlapping load: the pool's capacity covers the aggregate, and individual databases draw from it as needed.

The pool is priced on its provisioned capacity, not per database. In the vCore model, you pay per pool vCore-hour, roughly $0.1129/vCore-hour for General Purpose Gen5, plus pool storage per GB-month. A 4-vCore GP pool runs about $330/month for compute regardless of whether it holds 5 databases or 50. The DTU model is similar but measured in eDTUs. Databases added to the pool don't each incur a separate compute charge.

c3x reads sku_name (the performance tier) and the pool's vCore or DTU capacity and prices it at 730 hours/month, plus pool storage. The savings come from consolidation: if you'd otherwise run many small single databases each with idle headroom, a pool sized to the aggregate peak is cheaper.

Terraform example

A minimal but realistic configuration that C3X can estimate.

resource "azurerm_mssql_elasticpool" "shared" {
  name                = "shared-pool"
  resource_group_name = azurerm_resource_group.db.name
  location            = "eastus"
  server_name         = azurerm_mssql_server.main.name

  sku {
    name     = "GP_Gen5"
    tier     = "GeneralPurpose"
    family   = "Gen5"
    capacity = 4
  }

  max_size_gb = 100

  per_database_settings {
    min_capacity = 0
    max_capacity = 2
  }
}

Pricing dimensions

What you actually pay for when you provision azurerm_mssql_elasticpool.

Dimension	Unit	What's being charged
Pool vCores	per vCore-hour	Provisioned pool compute, shared by all databases in the pool. c3x prices the capacity at 730 hours/month. $0.1129/vCore-hour (GP Gen5)
Pool storage	per GB-month	Storage allocated to the pool (max_size_gb), shared across databases. $0.115/GB-month

Sample C3X output

Example output from c3x estimate (4-vCore GP pool, 100 GB):

azurerm_mssql_elasticpool.shared
├─ Pool vCores (GP Gen5, 4)   2,920  vCore-hours    $329.67
└─ Pool storage               100  GB-month          $11.50

OVERALL TOTAL                                        $341.17

Optimization tips

Common ways to reduce azurerm_mssql_elasticpool cost without changing the workload.

Pool databases with non-overlapping peaks

Consolidation vs separate DBs

Elastic pools save money when member databases peak at different times, so the pool's capacity covers the aggregate, not the sum of individual peaks. Databases that all spike together don't benefit.

Right-size pool capacity to aggregate peak

Proportional to over-provisioning

Provision pool vCores for the combined peak demand, not the sum of each database's max. Monitor pool utilization and trim capacity that stays unused.

Apply Azure Hybrid Benefit and reservations

Up to ~50% combined

Pools support Azure Hybrid Benefit (license savings) and reserved capacity, stacking the same ~30-40% and ~30% discounts as single databases.

FAQ

How does c3x estimate an elastic pool?

It reads sku_name and the pool's vCore (or DTU) capacity and prices it at 730 hours/month, plus pool storage. The pool is billed on its provisioned capacity, not per member database.

Do databases in the pool cost extra?

No. Member databases share the pool's provisioned compute and storage; they don't each incur a separate compute charge. That sharing is the whole point of a pool.

When is a pool cheaper than separate databases?

When you have many databases with uneven, non-overlapping load. The pool covers the aggregate peak instead of each database carrying its own idle headroom. For a few steadily-busy databases, single databases may be simpler and comparable.

Does the estimate change for the DTU model?

The model is analogous: DTU pools bill per eDTU. c3x reads the tier and capacity and prices accordingly. The vCore model is more common for new deployments.

Can I use Hybrid Benefit on a pool?

Yes. vCore-model pools support Azure Hybrid Benefit and reserved capacity, the same license and commitment discounts available to single databases and managed instances.