Handle PSD2/PSR payment initiation fallback when an ASPSP's dedicated API is unavailable: implement the contingency mechanism correctly

Steps

1. Detect API unavailability via HTTP 503, repeated 5xx, or timeout beyond the ASPSP's published SLA; log the failure timestamp and response code to establish a documented outage record
2. Check whether the NCA (National Competent Authority, e.g., FCA or BaFin) has granted the ASPSP an exemption from the fallback mechanism; if exempted, the ASPSP has no backup interface and you must surface a user-facing error
3. If no exemption applies, initiate the contingency fallback by navigating the user to the ASPSP's online banking interface; under PSD2 Article 33(6) / equivalent PSR provision, the ASPSP must allow screen-scraping-style access during certified API outages
4. Obtain prior NCA approval or EBA confirmation before activating the contingency mechanism in a non-outage situation; unauthorized use of the fallback outside a certified outage violates PSD2 Article 33
5. Record the start and end of every contingency access session; report prolonged API outages to the relevant NCA within the regulatory notification window specified by your home-state regulator
6. Re-test the primary dedicated API at regular intervals (e.g., every 5 minutes) and switch back as soon as it recovers; log the switchover for audit purposes