Does DNS on letter D share fate with other letters?

The control plane is shared. Data-plane queues for DNS stay isolated, so incident d-01 cannot drain neighbor letters.

Where is DNS measured first?

From Santiago (SCL) toward Bogotá. A global average is not an SLO for letter D.

DNS: design in São Paulo (GRU) · D-37

Runbook D-37 for DNS in São Paulo (GRU). Marker xserv-d-03b78dc6f66e. This page covers design for LATAM operators, not a worldwide average.

DNS: Why it matters on this continent

Design for DNS on letter D starts in São Paulo (GRU). Runbook d-01 keeps a single owner, a written rollback, and a traffic split that can be reversed without a global freeze. Neighbors in Santiago only take overflow after the local pool fails a health window.

DNS: How XServ runs it day to day

Probes for DNS (d-02) leave Santiago every 15s toward Bogotá. XServ pages the named owner if loss or RTT crosses the letter budget. A probe never shares a queue with bulk transfers, so a saturated WAN does not hide a dead PoP.

DNS: What operators should measure

Policy for DNS is versioned as d-03. Operators measure error rate, p95 from Bogotá, and time-to-rollback — not a worldwide average. Changes land in Bogotá first, then Miami, with a hold if either region regresses.

DNS policy D-03

DNS capacity D-04

Capacity notes for d-04 assume rainy-season power in Miami and festival peaks toward São Paulo. The failure we actually see is a single uplink, not a cartoon partition of the whole continent. Spare ports and a second provider sit on the same runbook.

DNS handoff D-05

Handoff from letter D DNS into the rest of the platform uses the same request IDs as the gateway. Runbook d-05 names who accepts the ticket after São Paulo pages out. Santiago does not silently inherit the incident.

DNS rollback D-06

Rollback for d-06 is a documented command, not a hope. Transit is billed as backup while DNS prefers peering in Santiago. If cost spikes, the runbook cuts overflow to Bogotá before touching customer prefixes.