Azure AI Search cost: you pay for provisioned search units
Azure AI Search (formerly Cognitive Search) bills by tier and search units, provisioned by the hour regardless of query volume. Replicas and partitions multiply the cost. Here is how units price and how to size them for cost and performance.
Quick answer
Azure AI Search bills by tier (Basic around $73/month, Standard S1 around $245/month) and by search units, where search units equal replicas times partitions. Capacity is provisioned by the hour regardless of query volume, so replicas (for query throughput and availability) and partitions (for index size) each multiply cost. Size to real need.
Azure AI Search provides a managed search index. It is a provisioned service: you pay for allocated capacity by the hour, not per query, so the bill is set by the tier you choose and how many search units you run.
Tier sets the base
Each tier has a fixed hourly rate and defined limits on index size, replicas, and partitions. Basic is around $73 a month; Standard S1 around $245; higher Standard and Storage-Optimized tiers cost more for larger indexes and higher throughput. The tier is your entry price.
Search units multiply it
| Factor | Provides | Cost effect |
|---|---|---|
| Replicas | Query throughput, availability | Multiplies units |
| Partitions | Index size, indexing throughput | Multiplies units |
Billable search units equal replicas times partitions. Two replicas and two partitions is four search units, four times the single-unit rate. You add replicas for query load and availability, and partitions for larger indexes, so both scale cost directly.
Sizing for cost and performance
Start with the minimum units the workload needs: enough partitions to hold the index and enough replicas to meet query throughput and any availability SLA (three replicas for a read SLA). Adding replicas improves query performance and resilience but costs proportionally, the same cost-versus-performance tradeoff as optimizing p95 and cost. Scale down in non-production, and do not over-provision partitions for an index that is small today.
FAQ
How is Azure AI Search priced?
By tier and search units. Each tier has a fixed hourly rate (Basic around $73 per month, Standard S1 around $245), and billable search units equal replicas times partitions. Capacity is provisioned by the hour regardless of query volume.
What is a search unit?
The billing unit for Azure AI Search, equal to replicas times partitions. Two replicas and two partitions is four search units. Replicas add query throughput and availability; partitions add index size and indexing throughput. Both multiply cost.
How do replicas and partitions affect cost?
They multiply it. Billable units are replicas times partitions, so each additional replica or partition adds a full unit's cost. Add replicas for query load and availability and partitions for index size, sizing each to real need rather than a comfortable default.
How do I reduce Azure AI Search cost?
Choose the lowest tier that holds your index and meets throughput, provision the minimum replicas and partitions the workload needs, scale down in non-production, and avoid over-provisioning partitions for a small index. Units are provisioned hourly, so unused capacity is pure cost.
Does Azure AI Search charge per query?
No. It is a provisioned service billed by allocated capacity (tier and search units) by the hour, not per query. This means an idle index costs the same as a busy one, so sizing capacity to real need is the main cost control.
Does C3X estimate Azure AI Search cost?
C3X prices the azurerm_search_service resource, its SKU, and its replica and partition counts from your Terraform, so the provisioned search-unit cost appears before deploy.
What to do next
Size your search service before you deploy. C3X reads your Terraform and prices Azure AI Search and the rest of your stack against a live catalog. Start with the quickstart.
Pricing references
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