Scenarios

Three services, one ramp

Payment idempotency change touching gateway, ledger, and notification services at once. Outcome: zero drift · one 40-min hold. 4 held · 1 adaptation (40-min hold) · 0 escapes

idempotency-three-services

Three services, one ramp

Payment idempotency change touching gateway, ledger, and notification services at once.

ZERO DRIFT
The plan — drafted before anyone saw it
Strategy Three control points, one coordinated ramp — advance together or not at all
Control points payment-gw · ledger · notifier, in lockstep
Gates cross-service contract check · synthetic idempotency probes
Guardrails drift between services · ledger p99 (breached twice at 25% before)
Rollback any one service breaches → all three step back
Ramp — planned outline, actual fill
5%
25%
50%
100%
The run — from the decision log
T+0m read: diff crosses payment-gw, ledger, notifier — one shared idempotency contractheld
T+1h read: ledger breached twice at 25% before; gateway never hasheld
T+3h chose: coordinated ramp with the tightest gate on ledgerheld
T+1d held: ledger p99 wobbled at 25% — a 40-minute hold, then cleanadapted
T+2d done: contract shipped with zero cross-service driftheld
4 held · 1 adaptation (40-min hold) · 0 escapes

learnedledger breaches at 25% — future ledger ramps soak longer there.