# Checkout blocked for segment: pre-release checklist

Source: https://releasefailures.com/incidents/checkout-blocked-for-segment/
Content version: 1.0.0
Verified on: 2026-10-21
Licence: CC BY 4.0

Definition: A checkout step fails for one customer segment, country or card type after a release.
- [ ] PR-01 Add validator unit cases for a four-digit Argentine postcode such as 1213 and run them on every bump of the postcode validation package. (test class: Unit tests)
- [ ] PR-02 Add a unit case for each country that has no entry in the shared postcode rules file and therefore falls back to the validation package. (test class: Unit tests)
- [ ] PR-03 Run the client-side validator unit tests with one server-accepted sample postcode per country. (test class: Unit tests)
- [ ] PR-04 Run the checkout flow end to end with one saved address per shipping country, including an Argentine address with a four-digit postcode. (test class: End-to-end tests)
- [ ] PR-05 Place an end-to-end test payment through the temporary (CSE) token workflow before switching the gateway integration version. (test class: End-to-end tests)
- [ ] PR-06 Add a canary alert on the 4xx rate of payment requests alongside the 5xx alert. (test class: Canary and progressive delivery checks)
- [ ] PR-07 Split canary payment error rates by gateway token workflow before promoting a gateway integration change. (test class: Canary and progressive delivery checks)