AI for Coding: Plan a Zero-Downtime Database Migration

End-of-lesson check

15 questions · take it digitally for instant feedback at tendril.neural-forge.io/learn/quiz/end-ai-coding-database-migration-plan-r8a1-creators

1. In an expand-migrate-contract database migration, what happens during the 'contract' phase?

   1. Data is copied from the old schema to the new schema in batches
   2. Traffic is switched from the old system to the new system
   3. The old schema and any temporary columns are removed after validation
   4. New columns or tables are added to support both old and new schemas

2. Which task is AI particularly well-suited to help with when planning a database migration?

   1. Detecting lock contention based on your actual workload
   2. Predicting exactly how long the backfill will take in production
   3. Enumerating every code path that reads or writes the affected column
   4. Running the actual migration against a production database

3. A developer asks an AI tool to estimate how long a backfill of 10 million rows will take. The AI estimates 10 minutes. Why might this estimate be dangerously wrong?

   1. The AI confused megabytes with rows and recalculated incorrectly
   2. The database automatically rejected the backfill because it exceeded a size limit
   3. The estimate ignores index bloat, replication lag, and concurrent traffic on the database
   4. The AI used a randomized algorithm instead of actual row counts

4. What is a critical limitation of using AI to plan a database migration?

   1. AI cannot identify which columns are affected by the schema change
   2. AI cannot run the migration against your actual production database
   3. AI cannot generate rollback steps for each migration phase
   4. AI cannot understand the difference between read and write operations

5. During the dual-write phase of an online migration, what exactly happens?

   1. The database is locked to prevent any writes during schema changes
   2. The old schema is deleted and all data is rewritten to the new schema
   3. All traffic is redirected to the new schema while keeping the old one as backup
   4. Data is written to both the old and new schemas simultaneously before cutting over

6. Why should each phase of a zero-downtime migration include a documented rollback procedure?

   1. If something goes wrong, you can quickly return to the known-good state without guessing
   2. Modern databases automatically rollback and no manual procedures are needed
   3. Rollback procedures make the migration run faster by skipping validation steps
   4. Rollback is only needed if the AI-generated plan contains errors

7. Before cutting over to a new database schema, why is it important to identify all code paths that read or write the affected column?

   1. To ensure every application that uses that data is updated to use the new schema
   2. So the code can be deleted and replaced with AI-generated code
   3. So the database can automatically optimize queries for the new schema
   4. To determine which programming language to use for the migration

8. Why is testing a migration plan on a staging database clone of production data essential, even after using AI to create a detailed plan?

   1. Real-world workloads and data patterns reveal issues that estimates cannot predict
   2. AI plans always work perfectly and staging proves the AI was correct
   3. Staging tests are required by law for all database changes
   4. Staging databases automatically optimize the migration for production

9. What specific risk cannot be accurately predicted by AI when planning a database migration?

   1. Which programming languages are used in the codebase
   2. Lock contention caused by your specific workload patterns
   3. The number of affected rows in the database
   4. The names of the columns being modified

10. What should serve as an observable success signal for a backfill phase of a database migration?

    1. A specific count of rows migrated matches the expected count in the target table
    2. The AI tool reports that the plan was generated successfully
    3. The database server's CPU usage drops to zero
    4. The application code has been deployed to production

11. In the context of zero-downtime migrations, what is the primary goal of the 'expand' phase?

    1. To add new columns or tables that can coexist with the old schema
    2. To switch all traffic from the old system to the new system
    3. To copy all existing data from the old schema to the new schema
    4. To remove the old schema and contract the database size

12. A developer relies solely on AI's estimated backfill time of 15 minutes and schedules a quick maintenance window. The actual migration takes 3 hours. What is the most likely cause?

    1. The developer misunderstood the AI's output language
    2. The database password expired during the migration
    3. Real-world factors like index bloat, replication lag, and production traffic extended the duration
    4. The AI deliberately provided incorrect information

13. What does 'zero-downtime' migration actually mean in practice?

    1. The migration happens instantly in zero seconds
    2. The database is never locked or unavailable during the migration
    3. No users are affected because the database is turned off briefly
    4. Applications can continue serving users while the migration happens underneath

14. What is the difference between a 'backfill' and a schema 'migration' in database terminology?

    1. Backfill is faster than migration and requires no planning
    2. Backfill only works on empty tables, migration works on populated tables
    3. Backfill and migration are identical terms for the same process
    4. Backfill moves data between schemas, migration changes the schema structure

15. When should a rollback be executed during a zero-downtime migration?

    1. Rollback should be avoided at all costs because it wastes time
    2. Only when critical failures occur that cannot be quickly fixed, and when rollback is faster than debugging
    3. When any minor error appears in the application logs
    4. Immediately after the migration completes successfully