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Schema Migrations -- Testing the Riskiest Deployment
9.1🔒What Makes Migrations RiskySchema migrations are one of the riskiest deployment operations. A bad migration can cause data loss, corruption, or extended downtime…
9.2🔒The Migration Testing Checklist
9.3🔒Testing Migrations with Shell Scripts
9.4🔒Testing Migrations in Python
9.5🔒Performance ConsiderationsAdding an index to a table with millions of rows can lock the table for minutes:
9.6🔒Migration Testing in CI
9.7🔒ExercisesBeginner:
9.8🔒Q&AResume phrasing- Established a schema migration testing pipeline in CI that validates apply, rollback, and data preservation for every migration before it…
9.9🔒Q&ACover letter framingSchema migrations are the highest-risk deployment operation in most systems. I treat every migration as a potential data loss event and…
9.10🔒Q&AInterview framing"I approach migration testing with a checklist: apply cleanly, rollback cleanly, preserve existing data, complete in acceptable time, and…
9.11🔒Q&AWhat not to say- "I test migrations on an empty database." -- This misses data preservation issues and performance problems. - "I do not write rollback…
9.12🔒Q&AQuestion 1Prompt: You need to add a NOT NULL column called phone_verified (boolean) to a users table with 5 million rows. The team wants to deploy…
9.13🔒Q&AQuestion 2Prompt: A migration renames the column email to email_address on the users table. After deploying the migration to staging, the application…
9.14🔒Q&AQuestion 3Prompt: Your CI pipeline runs migration tests against an empty database, and they always pass. But in staging (which has 2 years of…