API Design · Senior · Question 25 of 75

What are the backward-compatibility rules for Protocol Buffers messages?

1Field numbers can be renumbered freely
✓Correct answer: Never change or reuse field numbers, add new fields with new numbers, and reserve numbers and names of removed fields
3Renaming a field breaks the wire format

Explanation

Protobuf encodes field numbers, not names, so renaming is wire-safe, but renumbering corrupts data between versions.

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