PlanetScale Database Migration: AI-Optimized Technical Reference

Executive Summary

PlanetScale migration is significantly more complex than marketing suggests. Foreign keys are completely eliminated, stored procedures must be rewritten, and "zero downtime" migrations still involve 30-60 seconds of connection drops. Expect 3-6 months for non-trivial migrations with multiple failure attempts.

Critical Prerequisites

Required Configuration Check

SHOW VARIABLES WHERE Variable_name IN ('log_bin', 'gtid_mode', 'binlog_format');

Breaking Points:

• log_bin = OFF: Forces manual migration with downtime
• gtid_mode = OFF: Import Tool unusable
• binlog_format != ROW: Causes replication failures

Migration Blockers Assessment

-- Foreign keys requiring application logic rewrite
SELECT COUNT(*) FROM information_schema.KEY_COLUMN_USAGE
WHERE REFERENCED_TABLE_NAME IS NOT NULL;

-- Stored procedures requiring complete rewrite
SELECT ROUTINE_TYPE, ROUTINE_NAME FROM information_schema.ROUTINES
WHERE ROUTINE_SCHEMA = 'your_database';

-- Triggers requiring application migration
SELECT TRIGGER_NAME, EVENT_MANIPULATION FROM information_schema.TRIGGERS
WHERE TRIGGER_SCHEMA = 'your_database';

-- FULLTEXT indexes requiring external search
SELECT TABLE_NAME, INDEX_NAME FROM information_schema.STATISTICS
WHERE INDEX_TYPE = 'FULLTEXT';

Migration Method Decision Matrix

Database Size	Binlogs Available	Downtime Tolerance	Recommended Method	Actual Timeline
< 10GB	Yes	None	Import Tool	30-60 minutes
< 10GB	No	Acceptable	Manual migration	2-3 hours
10GB - 1TB	Yes	None	Import Tool	1 day - 1 week
10GB - 1TB	No	Acceptable	CLI migration chunks	Weekend project
> 1TB	Yes	None	Import Tool + support	1+ weeks
> 1TB	No	Any	Professional services	Months

Method-Specific Failure Modes

Import Tool (PlanetScale's "Zero Downtime" Option)

Reality: 30-60 seconds connection drops, not zero downtime

Common Failures:

• Binlog retention gaps during migration
• Network timeouts on large table copies
• MySQL features confusing Vitess routing
• Progress indicators lying about completion time

Requirements:

• Binary logging: log_bin = ON
• GTID mode: gtid_mode = ON
• Row format: binlog_format = ROW
• Retention: expire_logs_days >= 3
• Permissions: SUPER privilege required

CLI Migration (pscale)

Use Cases:

• Import Tool fails on edge cases
• Scripted multi-database migrations
• Detailed logging requirements

Failure Points:

• Authentication expires mid-migration
• 2-hour timeout limit on restores
• Error 2013: Lost connection on large datasets
• Progress reporting completely inaccurate

Manual Export/Import

When Required:

• Database under 10GB with acceptable downtime
• Binlog configuration impossible to fix
• Previous methods failed

Timeline Reality:

• Export: 10-20 minutes per GB
• Import: 15-30 minutes per GB on PlanetScale
• Testing: 4-6 hours minimum for responsible verification

Resource Requirements

Technical Expertise

• Database Team: 2-4 weeks planning and testing
• Application Developers: 1-6 months rewriting foreign key logic
• DevOps: 2 weeks CI/CD pipeline rewrites
• Project Management: Coordinate 3x longer timelines than estimated

Infrastructure Prerequisites

• Binlog retention minimum 3 days
• Network bandwidth for data transfer
• Backup verification systems
• Rollback database maintenance

Critical Code Changes Required

Foreign Key Elimination

Impact: All referential integrity moves to application code

-- Generate foreign key removal statements
SELECT CONCAT('ALTER TABLE ', TABLE_NAME, ' DROP FOREIGN KEY ', CONSTRAINT_NAME, ';')
FROM information_schema.KEY_COLUMN_USAGE
WHERE REFERENCED_TABLE_NAME IS NOT NULL;

Application Rewrite Requirements:

• Convert ON DELETE CASCADE to application logic
• Add validation before insert/update operations
• Handle race conditions previously prevented by constraints
• Test edge cases database previously blocked

Timeline: 1-6 months depending on foreign key count and complexity

Stored Procedure Migration

Reality: Complete rewrite required, no compatibility layer

Assessment Questions:

• Business logic vs convenience code distinction
• Edge case handling in procedures
• Performance under application-level load
• Documentation of original logic availability

Performance Impact Assessment

Expected Degradation

• Initial Latency: 10-20% increase due to Vitess routing overhead
• Query Performance: Varies significantly by query type
• Connection Pooling: Requires complete reconfiguration
• Cache Behavior: Cold caches after migration

Optimization Requirements

• Query routing awareness for cross-shard operations
• Index optimization more critical than single MySQL
• Batch operation sizing adjustments
• Connection pool parameter tuning

Operational Changes

Schema Management

New Workflow:

pscale branch create my-app feature-branch
pscale deploy-request create my-app feature-branch
pscale deploy-request deploy my-app 123 --wait

Impacts:

• No direct ALTER TABLE statements
• Emergency schema changes require approval workflow
• CI/CD pipeline complete rewrite necessary

Monitoring Changes

• PlanetScale Insights replaces existing query monitoring
• Alert threshold recalibration required
• Prometheus integration for custom metrics
• 48-hour intensive monitoring post-migration

Backup Strategy

• Automated backups replace manual procedures
• Point-in-time recovery through PlanetScale interface
• Manual backup via pscale database dump
• Disaster recovery becomes vendor-dependent

Real-World Timeline Expectations

Small Database (< 10GB)

• Planning: 2-4 weeks
• Foreign Key Rewrite: 1-2 weeks
• Migration Execution: 1 day - 1 week (multiple attempts)
• Stabilization: 1-2 weeks minimum
• Total: 2-3 months

Medium Database (10GB - 1TB)

• Planning: 1-2 months
• Application Rewrites: 1-2 months
• Migration Attempts: 1-2 weeks
• Stabilization: 1+ months
• Total: 4-6 months

Large Database (> 1TB)

• Total Timeline: 6+ months to 1 year
• Professional Services: Recommended
• Multiple Migration Weekends: Expected
• Rollback Planning: Critical requirement

Critical Warnings

Database Features Not Supported

• Foreign key constraints (eliminated)
• Stored procedures (complete rewrite required)
• Triggers (application logic migration)
• FULLTEXT indexes (external search required)
• Custom MySQL functions (compatibility verification needed)

Hidden Costs

• Row-based billing accumulation
• Developer time for application rewrites
• Extended testing periods
• Potential performance optimization requirements
• Migration tool failures requiring restarts

Vendor Lock-in Considerations

Exit Difficulty: High due to:

• 100,000 row query limits for export
• No binary log access for real-time replication
• Password restrictions breaking standard tools
• Branching workflow dependencies

Case Study: FeatureOS migration away from PlanetScale in 2025

• Used mydumper to escape row limits
• Migrated to PostgreSQL via bridge MySQL instance
• 50% cost reduction achieved
• Significant performance improvements reported

Success Criteria

Technical Metrics

• Application error rates return to baseline
• Query performance stabilizes within 20% of original
• No 3am pages for database issues
• Data integrity verification passes

Operational Metrics

• Team comfortable with branching workflow
• Monitoring alerts properly calibrated
• Rollback procedures tested and documented
• Business stakeholders satisfied with stability

Emergency Procedures

Rollback Decision Points

• Data integrity issues discovered
• Performance degradation exceeds 20% after 1 week
• Application errors persist beyond stabilization period
• Business impact exceeds migration benefits

Rollback Execution

Before Cutover: Stop process, original database untouched
After Cutover: Complex due to dual-write implications

• Reverse replication may be available
• Data consistency verification required
• Application downtime likely during rollback

Essential Resources

• Import Tool Documentation: Database import process details
• MySQL Compatibility Reference: Vitess feature support matrix
• CLI Documentation: Complete pscale command reference
• Foreign Key Migration Guide: Application logic conversion patterns
• Community Support: Discord and GitHub for real-world assistance
• Professional Services: For databases > 1TB or complex requirements

Risk Mitigation

Pre-Migration

• Comprehensive foreign key inventory and rewrite planning
• Stored procedure documentation and conversion strategy
• Performance baseline establishment
• Rollback procedure documentation and testing

During Migration

• Multi-attempt planning with checkpoint understanding
• Network stability verification
• Progress monitoring with realistic expectations
• Support contact preparation for complex issues

Post-Migration

• Intensive monitoring for 48+ hours
• Performance optimization iteration
• Team training on new operational procedures
• Documentation updates for new workflow patterns