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Cache hit ratio (CHR) is the single most important CDN metric. It’s the share of requests served straight from the edge cache, with no origin round-trip. High CHR means lower latency, lower origin load, and a smaller bill.
Cache Hit Ratio

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How it’s calculated

cache_hit_ratio = cache_hits / (cache_hits + cache_misses)
A MISS becomes a HIT after the first request fills the cache. A path that’s only ever requested once is always a MISS and drags CHR down — that’s normal for long-tail content.

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What “good” looks like

WorkloadHealthy CHRInvestigate
Static assets (/static/*)95–99%< 90%
Image library90–98%< 85%
HLS / DASH VOD90–97%< 85%
Mixed (HTML + API + assets)75–90%< 65%
API-heavy (short TTL)30–70%wildly variable
Don’t chase a single number — chase trend stability per path class.

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Read the chart

ElementMeaning
Main %Hit ratio over the window.
Trend lineRolling CHR — sudden drops point at deploys, purges, or noisy keys.
Comparison %Change vs prior period.

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Pull via API

curl -sS "https://api.tenbyte.io/cdn/distributions/$DISTRIBUTION_ID/analytics/cache?from=2026-05-01T00:00:00Z&to=2026-05-09T00:00:00Z" \
  -H "Authorization: Bearer $TENBYTE_API_TOKEN" | jq

{
  "hits": 41510234,
  "misses": 3501112,
  "hit_ratio": 0.922,
  "series": [
    {"ts": "2026-05-01T00:00:00Z", "hit_ratio": 0.94}
  ]
}

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Diagnose a low CHR

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Tuning playbook

  1. Spot the bad prefix. Filter analytics by URL prefix; find the prefix dragging overall CHR down.
  2. Inspect a sample path. curl -sSI "$CDN_HOST/the/path" and look at cache-control, vary, and the cache rule that matches.
  3. Apply the right fix:
    • Origin sends private / no-store → enable Ignore Origin No Cache on the cache rule.
    • Query string is noisy → enable Ignore Query String in Cache Key.
    • Vary: User-Agent fragments cache → strip or narrow via response header rule.
    • TTL too short → bump expiration time.
  4. Validate. Wait for the cache to rewarm, then check CHR per path.

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Common false alarms

  • CHR drops right after a purge. Expected — every purged path becomes a MISS until refilled. Watch for recovery within minutes.
  • CHR drops on launch day. New paths haven’t filled the cache yet. Don’t tune; wait.
  • Low CHR on auth callbacks / per-user JSON. These are correctly uncacheable. Exclude them from your “should be cached” baseline.

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Operational tips

  • Track per-path-class CHR, not a single distribution-wide number — averages hide problems.
  • Alert on slope, not value. A 10-point drop in 5 minutes is incident-worthy; a slowly drifting baseline calls for tuning, not paging.
  • Pair with origin metrics. Origin CPU spikes that line up with CHR drops confirm causation.
  • Cache hit ratio + bandwidth answers “is this CDN paying off?” — the higher CHR, the more leverage.