Zero-Downtime Explained: When ALGORITHM=INSTANT Actually Works in Aurora MySQL

Database schema changes are a critical pain point for production systems, especially high-traffic applications where downtime directly translates to lost revenue. ALGORITHM=INSTANT promises zero-downtime migrations, but the reality is more nuanced—understanding which operations truly support this feature is essential for SREs managing continuous deployments. This article cuts through the misconceptions with practical guidance for leveraging this capability safely in production Aurora MySQL environments.