playbook/antigravity-awesome-skills/skills/vercel-optimize/references/support-topics/external-api-critical-path-platform.md

id	title	status	candidateKinds	frameworks	priority	citations	maxBriefChars
external-api-critical-path-platform	Cross-framework external API critical path	active	external_api_slow	*	86	https://vercel.com/docs/functions/debug-slow-functions https://vercel.com/docs/caching/runtime-cache https://vercel.com/docs/functions/functions-api-reference/vercel-functions-package	850

Investigation Brief

External API candidates are actionable only when the slow hostname is on a customer route's critical path. Prove the route waits on it before suggesting a cache, payload, or post-response change.

Evidence To Check

Use hostname latency, caller routes, transfer bytes, and source awaits. Check sequential calls, overbroad payloads, repeated shared data, and side effects that can move after the response.

Do Not Recommend When

Do not cache mutations, secrets, per-user responses, or unknown freshness contracts. Do not blame Vercel runtime when the upstream owns the latency.

Verification

Name the hostname, caller route, observed p75/p95 or bytes, and exact await or fetch line that blocks the response.