Azure Cosmos DB – Consider Disabling Multiple Write Locations for Non-Production Projects

Azure Cosmos DB multi-region writes provide global distribution and high availability, but come with a significant cost premium. For non-production environments like development, staging, and testing, this additional expense is often unnecessary and can be easily optimized.

Detailed Cost Analysis

Cost Implications

• Single-Region Write: Approximately $58/month for 1000 RU/s

• Multi-Region Write: Approximately $117/month for 1000 RU/s

• Potential Savings: Up to 50% cost reduction

Performance and Cost Breakdown

• Multi-region writes incur a 2x pricing multiplier

• Unnecessary for environments that don’t require global write distribution

• Significant overhead for development and testing workloads

Implementation Guide

Infrastructure as Code Example (Terraform)

Before (Multi-Region Write)

resource "azurerm_cosmosdb_account" "example" {
  multiple_write_locations = true
  location                 = "westus"
  geo_location {
    location          = "eastus"
    failover_priority = 1
  }
}

resource "azurerm_cosmosdb_account" "example" {
  multiple_write_locations = true
  location                 = "westus"
  geo_location {
    location          = "eastus"
    failover_priority = 1
  }
}

resource "azurerm_cosmosdb_account" "example" {
  multiple_write_locations = true
  location                 = "westus"
  geo_location {
    location          = "eastus"
    failover_priority = 1
  }
}

After (Single-Region Write)

resource "azurerm_cosmosdb_account" "example" {
  multiple_write_locations = false
  location                 = "westus"
}

resource "azurerm_cosmosdb_account" "example" {
  multiple_write_locations = false
  location                 = "westus"
}

resource "azurerm_cosmosdb_account" "example" {
  multiple_write_locations = false
  location                 = "westus"
}

Manual Configuration Steps

Navigate to Azure Cosmos DB account settings

Locate “Multi-Region Writes” configuration

Disable multi-region write capabilities

Confirm single-region write configuration

Best Practices

Environment-Specific Configuration:

• Keep multi-region writes for production

• Disable for development and staging

• Regular Cost Review: Periodically audit Cosmos DB configurations

• Leverage Infracost: Use Infracost to automatically detect and flag multi-region write configurations in non-production environments

Example Scenarios

Scenario 1: Development Environment

Use Case: Backend service with minimal global requirements

Recommended Action: Single-region write

Potential Savings: $700-$1,400 annually per database

Scenario 2: Testing Infrastructure

• Use Case: Temporary project with localized testing needs

• Recommended Action: Disable multi-region writes

• Potential Savings: Immediate cost reduction

Considerations and Caveats

Potential Limitations

• Not suitable for globally distributed production applications

• May impact disaster recovery capabilities

Requires careful architectural planning

When to Maintain Multi-Region Writes

Global customer base

Strict latency requirements

Regulatory compliance mandating geographic distribution

Implementation Tooling

Recommended Tools

• Infracost: Automatically detect and recommend Cosmos DB configuration optimizations

• Azure Cost Management: Track and analyze database spending

• Terraform: Programmatically manage database configurations

Frequently Asked Questions (FAQs)

How much can I save by disabling multi-region writes?
Typically 40-50% of Cosmos DB operational costs for non-production environments.

Will disabling multi-region writes impact application performance?
For non-production environments, performance impact is minimal. Recommended only for dev/test scenarios

How do I know if multi-region writes are necessary
Assess your application’s global distribution requirements. Most development and staging environments do not require multi-region writes.

Can Infracost help me identify these cost optimization opportunities?
Yes! Infracost’s free trial includes automatic detection of multi-region write configurations and provides actionable cost-saving recommendations.

Are there any risks in changing Cosmos DB configurations?
Always test configuration changes in a staging environment first and verify application compatibility.