Data Retention Policy

Understanding data retention fundamentals

Data retention policies establish clear guidelines for how long different types of data should be stored and when they should be archived or deleted. For time-series data, these policies are particularly important because of the continuous nature of data ingestion and the varying requirements for data accessibility.

A typical retention policy might specify:

• Hot data retention period (recent, frequently accessed data)
• Warm data retention period (less frequently accessed historical data)
• Cold storage requirements (archived data for compliance)
• Data deletion schedules and procedures

Storage tiers and retention strategies

Modern time-series databases often implement cold vs hot storage strategies to optimize both cost and performance. This tiered approach allows organizations to maintain different retention periods based on data temperature:

Each tier typically has its own retention policy, reflecting the decreasing likelihood of data access over time.

Implementing retention policies

When implementing a data retention policy, several key factors need consideration:

Regulatory requirements

Financial institutions must often retain certain data for specific periods to comply with regulations:

• Trade data retention for market surveillance
• Customer transaction records
• Audit trails for compliance reporting

Performance impact

Retention policies directly affect database performance through:

• Query latency across storage tiers
• Storage tiering efficiency
• Resource utilization for data movement

Cost optimization

Organizations can optimize storage costs by:

• Automatically moving older data to cheaper storage
• Implementing compression strategies
• Deleting unnecessary data systematically

This creates a table with a 90-day retention period, automatically managing data lifecycle.

Best practices for retention policy design

1. Define clear objectives

   • Business requirements
   • Regulatory compliance needs
   • Performance targets
   • Cost constraints

2. Implement monitoring

   • Track data volume growth
   • Monitor storage utilization
   • Verify policy enforcement
   • Alert on retention failures

3. Document procedures

   • Data classification guidelines
   • Retention schedules
   • Archive processes
   • Emergency restoration procedures

Impact on system design

Retention policies influence several aspects of system architecture:

Backup strategies

• Frequency of backups
• Retention of backup copies
• Recovery point objectives

Storage architecture

• Storage tiering configuration
• Archive storage solutions
• Compression strategies

Query optimization

• Partition pruning effectiveness
• Index maintenance
• Query planning across storage tiers