An API rollout supports rapid routing rollback, but a database migration removes columns still used by the old version. What is the best corrective design?

Choose the single best answer.

A.Use expand-and-contract schema evolution so both application versions remain compatible during rollout
B.Increase API rate limits to prevent schema incompatibility
C.Treat blue-green duplicate capacity as a guarantee of schema reversibility
D.Assume switching traffic back recreates deleted columns and data

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✓ Correct answer

Use expand-and-contract schema evolution so both application versions remain compatible during rollout

Expand-and-contract retains compatible schema until the old version is retired. Traffic rollback does not restore removed data, duplicate environments do not make their shared schema reversible, and rate controls do not repair incompatible contracts. Source guide: PDF page(s) 54.

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