Fintech Apex Domain Support in Node.js: 3 Customer Record Cutover Rules

The source material outlines best practices for handling customer domain support in fintech onboarding using standard DNS configurations. Key points include:

1. Publish an A record for the apex domain (e.g., example.com) and a CNAME for www.example.com. An A record is preferred over a CNAME at the apex due to DNS limitations.

2. Verify both records before completing the onboarding process. This ensures the customer can access the service at either example.com or www.example.com.

3. The onboarding contract should track three states: the expected apex A record, the expected www CNAME, and the observed verification result. The verification result should include the hostname checked, expected type, normalized answer, observation time, and a bounded status like "pending" or "verified".

4. Retention of DNS verification data should be balanced. Storing every raw response creates large volumes (e.g., 6 GB for 100,000 attempts with 60 polls each). Instead, store a current result per hostname and transitions between states, along with aggregate metrics to analyze capacity and propagation.

5. The recommended apex support approach is an A record for the apex domain and a CNAME for www. Managed DNS providers offer proprietary apex indirection that is not portable. The instructions focus on a portable contract of apex A plus www CNAME.

In summary, the key recommendation is to use an A record for the apex domain and a CNAME for www, with verification tracking and retention focused on minimal, meaningful data to support onboarding and troubleshooting without creating unnecessary coupling or storage burdens.