Multi-Region TTFB, Origin Timeout & CDN Cache-Bypass Watchdog

2. Four Origin Latency & Cache-Bypass Guardrails (Next.js App Router / Vercel Serverless SSR)

Primary Failure Mode: Serverless function cold-starts, uncached RSC data fetches, and synchronous third-party CRM/Auth calls delaying Time-to-First-Byte.

• 1. Cache-Busting Origin Probe (/contact?_cb=timestamp): Appends a unique cache-bypass query token and Cache-Control: no-cache header so probes measure true origin compute & database TTFB rather than a 30ms CDN edge hit.
• 2. Phase-Split Timing Decomposition (DNS / TCP / TLS / TTFB): Separates DNS resolution, TCP connect, TLS 1.3 handshake, and server processing time to pinpoint whether latency comes from network routing or origin bottlenecks (Serverless function cold-starts, uncached RSC data fetches, and synchronous third-party CRM/Auth calls delaying Time-to-First-Byte.).
• 3. Soft-Degradation Warning Before HTTP 502/524 Outages: Triggers an early engineering alert when uncached TTFB exceeds 550ms for 3 consecutive checks—catching stuck worker pools before Cloudflare throws Error 524.
• 4. Multi-Region Verification (US-East, EU-Central, US-West): Confirm latency regressions from 2+ independent regions before paging on-call engineers to eliminate transient single-ISP packet loss false alarms.

# Measure True Uncached Origin TTFB & Phase Timings for apexclimate.com (Next.js App Router / Vercel Serverless SSR)
curl -sS -o /dev/null \
  -H "Cache-Control: no-cache, no-store" \
  -H "Pragma: no-cache" \
  -H "User-Agent: OnBits-Latency-Canary/1.0" \
  -w "http_code: %{http_code}\ncf_cache:  %header{cf-cache-status}\ndns_ms:    %{time_namelookup}s\ntcp_ms:    %{time_connect}s\ntls_ms:    %{time_appconnect}s\nttfb_s:    %{time_starttransfer}s\ntotal_s:   %{time_total}s\n" \
  "https://apexclimate.com/contact?_cb=$(date +%s)"

Multi-region cache-bypass assertion config (onbits-latency-watchdog.json):

{
  "watchdog_id": "origin_latency_guard_apexclimate.com",
  "stack": "nextjs",
  "target_url": "https://apexclimate.com/contact",
  "cache_bypass": {
    "append_timestamp_param": "_cb",
    "request_headers": {
      "Cache-Control": "no-cache, no-store",
      "X-OnBits-Synthetic": "latency-probe"
    }
  },
  "thresholds_ms": {
    "observed_baseline_ttfb_ms": 1450,
    "soft_warning_ttfb_ms": 550,
    "hard_critical_ttfb_ms": 1600,
    "consecutive_breaches_before_page": 3
  },
  "regions": ["us-east-1", "eu-central-1", "us-west-2"]
}