Write a Rollback-Safe Feature Flag
Added 2026-11-02
A flag is more than an if: default value, scope and a removal plan.
I am adding a flag to a new feature (details below). Design: 1) the default value and how it is read; 2) scope — per user, tenant or percentage — and why; 3) three metrics to watch once enabled, with abnormal thresholds; 4) the rollback action and expected recovery time; 5) the flag's lifecycle — what triggers removal and who owns it; 6) where this design is most likely to leave technical debt. No code, design only.
Site original
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How to use
功能开关的债，来自「上了就忘了删」。
Try tweaking it
- Have it restate requirements and constraints before writing code.
- Ask for the smallest change plus a rollback path, not a full-file rewrite.
What you should get
- A minimal, runnable change with copy-ready code
- Impact list: which files and call sites must follow
Common mistakes
- Asking it to touch ten files at once, then losing track of what broke what.
- Pasting only the error, with no code or version, and getting an unfixable answer.
How to check the output
- The change runs, can be rolled back, and touches nothing unrelated.
- Edge cases (empty, oversized, concurrent) are covered or explained.
Where it works
- Good for: having it restate requirements and constraints, then propose the smallest runnable change.
- Watch out: include versions and a minimal reproduction with the error, or the fix may look plausible but not fit.