Which practice provides a period during which old API versions remain usable after a new version is released?

• A. Deprecation windows
• B. Immediate migration
• C. Versionless endpoints
• D. Concurrent upgrades

Answer: (A)

A deprecation window is a defined grace period after a new API version is released during which older versions remain usable. This lets clients migrate over time, test compatibility, and update integrations without risking immediate downtime, while the service communicates which versions are slated for retirement and when. The window balances progress with stability, giving developers a predictable timeline to move to the new version before older versions are retired.

Immediate migration doesn’t provide any grace period, so clients would have to switch right away. Versionless endpoints remove versioning altogether, which eliminates the notion of a deprecated version rather than providing a transitional period. Concurrent upgrades refer to updating components at the same time, but they don’t inherently establish a formal window during which old versions stay usable after a new one is released.