Does WAN on letter W share fate with other letters?

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

Where is WAN measured first?

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

WAN: design in São Paulo (GRU) · W-37

Runbook W-37 for WAN in São Paulo (GRU). Marker xserv-w-5b1cc17d5c25. This page covers design for LATAM operators, not a worldwide average.

WAN: Why it matters on this continent

Design for WAN on letter W starts in São Paulo (GRU). Runbook w-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.

WAN: How XServ runs it day to day

Probes for WAN (w-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.

WAN: What operators should measure

Policy for WAN is versioned as w-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.

WAN cache W-08

Cache rules for WAN on w-08 keep language-correct objects near Miami. São Paulo is a sibling cache, not an origin. TTLs are short enough that a bad asset does not live through a weekend.

WAN headers W-09

Headers for w-09 carry the letter, the region (GRU) and a request id. WAN debugging in São Paulo should not require a packet capture in Santiago first.

WAN timeouts W-10

Timeouts on w-10 are tighter than the WAN RTT to Bogotá. WAN in Santiago fails fast and retries once; a third try needs a human because it is no longer a blip.

WAN regions W-11

Region names on w-11 match DNS and tickets: Bogotá / BOG, with Miami as the documented pair. WAN dashboards never say “LATAM” as if it were one RTT.