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
- 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