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
  }
}

# After (Single-Region Write)
resource "azurerm_cosmosdb_account" "example" {
  multiple_write_locations = false
  location                 = "westus"
}

Manual Configuration Steps

  1. Navigate to Azure Cosmos DB account settings
  2. Locate “Multi-Region Writes” configuration
  3. Disable multi-region write capabilities
  4. 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)

Typically 40-50% of Cosmos DB operational costs for non-production environments.

For non-production environments, performance impact is minimal. Recommended only for dev/test scenarios

Assess your application’s global distribution requirements. Most development and staging environments do not require multi-region writes.

Yes! Infracost’s free trial includes automatic detection of multi-region write configurations and provides actionable cost-saving recommendations.

Always test configuration changes in a staging environment first and verify application compatibility.