What You'll Get
The project brief promised a smooth weekend migration. Five servers, straightforward replication, minimal downtime. By Wednesday of week one, nothing worked correctly and the rollback plan had gaps no one noticed during planning.
This isn't a success story dressed up as a learning experience. This is a genuine failure analysis. The database replication lagged by 6 hours due to undocumented stored procedures. The application servers threw timeout errors because someone assumed the new subnet would have identical routing. DNS propagation took four times longer than estimated because the TTL values were set to 86400 seconds two years ago and forgotten.
We'll examine the actual incident logs, the Slack conversations where confusion spread, and the exact moment on day 12 when the team realized they needed to rebuild rather than fix. For skeptics who doubt those polished migration case studies, this shows what really happens when assumptions meet infrastructure reality.
Program Structure
Week-by-Week Failure Points
- Week 1: Initial Migration Attempt
- Replication begins Friday 11pm. By Saturday 4am, database lag exceeds acceptable threshold. Application layer timeout errors start Monday morning—root cause takes 3 days to identify.
- Week 2: Troubleshooting and Growing Problems
- DNS issues compound application errors. Load balancer health checks fail intermittently. Team discovers network ACLs blocking critical monitoring ports. Documentation proves incomplete.
- Week 3: Rebuild Decision and Recovery
- Day 12 decision point documented. Parallel rebuild initiated. Original migration officially abandoned day 16. New approach using staged cutover begins.
Evidence and Artifacts
- Unedited error logs from database replication showing 6-hour lag development
- Network packet captures revealing the subnet routing assumption failure
- Timeline of decision points with actual Slack message timestamps
- Configuration comparison showing the DNS TTL oversight