FORWARD compatibility could be defined as which statement?

FORWARD compatibility could be defined as which statement?

• A. Data produced using schema X can be read by consumers with schema X and X-2
• B. Data produced using schema X can be read by consumers with schema X or X-1
• C. Data produced using schema X can be read by consumers with X-1 only
• D. Data produced using schema X can be read by consumers with all previous schemas including X-1, X-2

Answer: (B)

Forward compatibility means that data written with a newer schema can still be read by older consumer code, at least by the immediately previous version, so that upgrades don’t break existing readers. The statement that data produced using a newer schema X can be read by consumers with schema X or X-1 captures this idea: the same-version reader can read the data, and the immediate older reader (X-1) can as well, preserving compatibility for existing deployments when you introduce a newer schema. It does not imply that much older versions (like X-2) will always be able to read it, which is why the other formulations don’t fit as well.

Forward compatibility means that data written with a newer schema can still be read by older consumer code, at least by the immediately previous version, so that upgrades don’t break existing readers. The statement that data produced using a newer schema X can be read by consumers with schema X or X-1 captures this idea: the same-version reader can read the data, and the immediate older reader (X-1) can as well, preserving compatibility for existing deployments when you introduce a newer schema. It does not imply that much older versions (like X-2) will always be able to read it, which is why the other formulations don’t fit as well.