MySQL Schema Migration Without Downtime: A Real Fintech Case Study

Schema changes on large MySQL tables can bring production systems to a halt if not handled correctly. This case study walks through how Mafiree helped a fintech client execute a zero-downtime MySQL schema migration on a 500M+ row production database — covering the real challenges faced, the three-phase tool strategy using gh-ost, pt-online-schema-change, and MySQL 8.0 INSTANT DDL, production configuration settings with performance benchmarks, and best practices for safely evolving your MySQL schema without impacting users

Jethish February 20, 2026

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FAQ

Yes. MySQL 8.0 supports several INSTANT and INPLACE DDL operations that modify schemas with minimal or zero locking. For operations that require a full table rebuild, tools like gh-ost and pt-online-schema-change enable zero-downtime migrations by creating a shadow copy of the table and applying changes in the background while the original table continues serving traffic. When should you call an expert? Mafiree’s MySQL consulting services can help you identify which operations are safe for native DDL and which require specialized tooling, saving you from unexpected downtime.

gh-ost uses MySQL’s binary log to capture changes and replicate them to a shadow table, avoiding triggers entirely. pt-online-schema-change uses database triggers to capture inserts, updates, and deletes on the original table and replay them on the shadow table. gh-ost generally offers better throttling and is less invasive, while pt-osc has broader compatibility with foreign keys and older MySQL versions.

Migration time depends on table size, row width, I/O capacity, and how aggressively you can throttle. As a benchmark, our 500M-row migration with gh-ost took approximately 4.5 hours with conservative throttling (nice-ratio=0.5). A similar table with no throttling on dedicated hardware could complete in 1.5–2 hours, but this is rarely safe for production.

Yes, with caveats. RDS supports both gh-ost (in “migrate-on-replica” mode) and pt-online-schema-change. However, RDS restricts SUPER privileges and direct filesystem access, so you need to configure tools accordingly. Mafiree has extensive experience running zero-downtime migrations on RDS, Aurora, and self-managed MySQL environments. Need help with RDS migrations? Contact our team for a tailored strategy.

Critical metrics include replication lag across all replicas, InnoDB buffer pool hit ratio, disk I/O utilization, active connection count, query latency at p95 and p99, and the migration tool’s progress output. A spike in any of these should trigger a pause or abort. Mafiree’s managed MySQL services include 24/7 monitoring of these metrics with automated alerting to ensure migrations complete safely. Explore our managed MySQL monitoring and consulting services to ensure your next migration runs smoothly.

Author Bio

Jethish

Jethish is a PostgreSQL DBA at Mafiree with expertise in building scalable, reliable, and high-performance database infrastructures. He focuses on PostgreSQL architecture, replication strategies, performance tuning, and high availability for mission-critical systems. Through his technical writing, he shares clear, practical insights on database internals, replication choices, load balancing, and cross-database integrations that help engineers and DBAs tackle real-world data challenges.