FA-73843 / Feature flag rollout bucketing / Member archive

Percentage rollout gate: User and flag swap places in the hash key · case 03

Users land in different buckets than every other SDK computes for the same flag.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

bucket = int(first 8 hex digits of sha1(salt + "." + flag + "." + user), 16) % 10000; the rollout percentage pct has at most two decimals and becomes a basis-point limit round(pct * 100); the user is enabled iff bucket < limit. Return [bucket, enabled].

Why this case matters

Percentage gates must be reproducible across services so the same user sees the same state everywhere.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
bucket exactly at limit is excluded (bob)	`[1447, true]`	`[2755, false]`	Failed

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