FA-1082 / Reliability / Member archive

Promote a standby after primary failure: Standby lag exceeds the declared data-loss allowance · case 02

The failover promote operation is admitted even though standby lag exceeds the declared data-loss allowance.

Member previewVariant 2 · 3 implementations · 9 checks per implementation

Case contract

Return a Boolean admission decision for promote a standby after primary failure. The record r must satisfy all of: r['primary_fenced'] is True; r['rpo_bound'][0]-r['rpo_bound'][1] <= r['rpo_bound'][2]; r['standby_writable'] is True; r['promotion_epoch'][0] > r['promotion_epoch'][1]; r['routing_switched'][0] == r['routing_switched'][1]. Extra tracing fields are ignored; validation does not mutate the record.

Why this case matters

A deterministic local contract for reliability. Each negative fixture violates exactly one invariant. No transport timing, persistence, cryptographic verification, or full protocol implementation is claimed.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
Standby lag exceeds the declared data-loss allowance	`true`	`false`	Failed

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