← Glossary / Cache Hit Rate

What is Cache Hit Rate?

Q: How do I know if I'm getting cached data?

Inspect the response headers. Look for CF-Cache-Status: HIT (Cloudflare), X-Cache: HIT (Fastly/AWS), or an Age header greater than 0. If these are present, the response was served from an intermediary, not the origin server.

Q: What is a Conditional GET?

It's an HTTP request that includes If-None-Match (with an ETag) or If-Modified-Since (with a timestamp). It asks the server: "Has this resource changed since I last saw it?" If it hasn't, the server returns a 304 status with no body, saving massive amounts of bandwidth.

Cache hit rate is the percentage of HTTP requests served directly from a cache—whether a CDN edge node, a proxy, or a local store—rather than requiring a full round-trip to the origin server. For data pipelines, cache dynamics dictate both extraction speed and data freshness. A high hit rate on the target's CDN means sub-50ms responses and lower anti-bot scrutiny, but introduces the risk of ingesting stale pricing or inventory data.

Network LayerCDNLatencyData FreshnessETag

// 02 — definitions

Speed vs.
staleness.

Understanding where a response actually came from is the difference between real-time data and yesterday's news.

Ask a DataFlirt engineer →

TL;DR

Cache hit rate measures efficiency: hits divided by total requests. In scraping, you encounter it in two places. Target-side caching (like Cloudflare edge nodes) speeds up your crawl but can serve outdated HTML. Client-side caching (your own pipeline) saves proxy bandwidth and compute by skipping redundant fetches for static assets.

01Definition & structure

Cache hit rate is the ratio of requests served from a cache compared to the total number of requests made. In the context of web scraping, it applies to two distinct layers: the target's infrastructure (CDNs like Cloudflare or Fastly) and your own pipeline's local storage. A "hit" means the cache had a valid, unexpired copy of the resource. A "miss" means the request had to travel all the way to the origin server to fetch fresh data.

02Target CDN caching

When you scrape a major website, you rarely hit their actual application servers. You hit an edge node. If the page is cached (a hit), the CDN returns it in milliseconds. This is great for crawler throughput and reduces the likelihood of triggering rate limits, as CDNs are designed to absorb massive traffic. However, the HTML you receive might be minutes or hours old, depending on the target's Cache-Control configuration.

03Local caching for scrapers

Sophisticated scraping pipelines maintain their own cache hit rate. By storing the raw HTML of fetched pages, developers can re-run extraction logic without making new network requests. In production, local caching combined with Conditional GETs ensures that you only download the full HTML body when the target server confirms the content has actually changed, drastically cutting residential proxy bandwidth costs.

04How DataFlirt handles it

We treat cache headers as a core component of pipeline orchestration. Our fetchers automatically store ETags and Last-Modified timestamps. On subsequent crawls, we issue conditional requests. If we get a 304, our extraction workers yield the known state. If a client requires absolute real-time data (e.g., financial feeds), we configure the pipeline to actively bust the target's cache, trading higher proxy usage for guaranteed data freshness.

05The staleness vs. cost tradeoff

There is an inherent tension between cache efficiency and data accuracy. Bypassing a CDN cache ensures you get the latest price, but it increases latency, consumes more proxy bandwidth, and significantly raises your risk of being flagged by anti-bot systems, as origin-bound traffic is scrutinized much more heavily than edge-served static assets.

// 03 — the math

Measuring cache
efficiency.

A 99% hit rate is excellent for a web server, but potentially disastrous for a pricing scraper if the cache TTL is 24 hours. We monitor hit rates to balance proxy costs against data freshness.

Cache Hit Rate = Hits / (Hits + Misses)

The standard efficiency metric. Higher means less origin load. Network Engineering 101

Effective Latency = (CHR × L_cache) + (1 − CHR) × L_origin

Pipeline speed is heavily skewed by the cache hit ratio. DataFlirt performance model

Cache Miss Probability = 1 / rank^α

Zipf's law applied to URL popularity. Long-tail pages always miss. Web caching distribution models

// 04 — header trace

Reading the
edge headers.

A scraper fetching a product page through a CDN. The first request is a MISS, pulling from origin. The second uses an ETag for a conditional GET, resulting in a 304 HIT.

CloudflareETag304 Not Modified

edge.dataflirt.io — live

CAPTURED

// Request 1: Cold fetch
GET /product/sku-992 HTTP/2
cf-cache-status: MISS
etag: "W/3f8c-b21a"
latency: 842ms // origin round-trip

// Request 2: Conditional fetch (15 mins later)
GET /product/sku-992 HTTP/2
if-none-match: "W/3f8c-b21a"
cf-cache-status: HIT
status: 304 Not Modified
latency: 41ms // served from edge
pipeline.action: use_local_cache

// 05 — cache busters

Why requests
miss the cache.

Factors that force a request to bypass the CDN edge and hit the origin server. For scrapers, intentionally busting the cache is sometimes necessary to guarantee data freshness.

AVG EDGE TTL · · · · 15–60 mins

MISS LATENCY · · · · 400–1200ms

HIT LATENCY · · · · 20–80ms

Query string variations

cache buster · Unique tracking params force origin fetches

Session cookies

auth bypass · Authenticated requests bypass public caches

Cache-Control directives

header rule · no-cache or max-age=0 sent by client

Geographic routing

cold edge · Hitting a POP that hasn't cached the asset yet

HTTP Method

POST/PUT · Mutating methods are never cached

// 06 — pipeline caching

Don't fetch twice,

unless the origin has changed.

DataFlirt implements aggressive client-side caching using Conditional GETs. We store the ETag and Last-Modified headers for every URL. On the next crawl cycle, we send those headers back. If the target CDN returns a 304 Not Modified, we skip the extraction phase entirely and yield the previous record. This drastically reduces proxy bandwidth, lowers our footprint on the target, and guarantees we only process actual state changes.

Local cache resolution

Pipeline state during a conditional re-crawl of a known URL.

url /catalog/item-42

request.headers If-None-Match: W/3f8c

response.status 304 Not Modified

proxy.bandwidth 124 bytes

extraction.phase skipped

pipeline.yield cached_record_v7

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intel, weekly.

Anti-bot shifts, scraping infrastructure updates, dataset delivery patterns, and business outcomes from our pipelines. Short, technical, no fluff.

// 07 — FAQ

Common
questions.

About caching mechanics, data staleness, cache-busting techniques, and how DataFlirt manages freshness SLAs.

Ask us directly →

How do I know if I'm getting cached data? +

Inspect the response headers. Look for CF-Cache-Status: HIT (Cloudflare), X-Cache: HIT (Fastly/AWS), or an Age header greater than 0. If these are present, the response was served from an intermediary, not the origin server.

How can a scraper bypass a target's CDN cache? +

The most reliable method is appending a random query parameter to the URL (e.g., ?cb=1716123456). You can also try sending Cache-Control: no-cache or Pragma: no-cache headers, though many modern CDNs are configured to ignore client-side cache directives to prevent DDoS attacks.

Why is a high cache hit rate bad for scraping? +

It's only bad if your use case requires real-time accuracy. If you are scraping spot pricing, airline tickets, or live inventory, a CDN serving a 15-minute-old page means you extract stale data. You get a fast response, but the business value of the data is compromised.

Should I cache responses locally in my scraping pipeline? +

Yes, absolutely. Local caching during development saves proxy costs and prevents you from hammering the target while debugging selectors. In production, use ETags to perform Conditional GETs. Let the target server tell you if your local cache is still valid via a 304 response.

What is a Conditional GET? +

It's an HTTP request that includes If-None-Match (with an ETag) or If-Modified-Since (with a timestamp). It asks the server: "Has this resource changed since I last saw it?" If it hasn't, the server returns a 304 status with no body, saving massive amounts of bandwidth.

How does DataFlirt handle cache staleness? +

During pipeline setup, we profile the target's cache TTL. If the TTL exceeds the client's data freshness requirements, we implement cache-busting techniques to force origin fetches. We absorb the latency hit to guarantee data accuracy, ensuring the delivered dataset reflects the true state of the origin.

$ dataflirt scope --new-project --target=cache-hit-rate READY

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hello@dataflirt.com · Bengaluru · IST · typical reply < 4h

What is Cache Hit Rate?

Speed vs.staleness.

TL;DR

Measuring cacheefficiency.

Reading theedge headers.

Why requestsmiss the cache.

Query string variations

Session cookies

Cache-Control directives

Geographic routing

HTTP Method

Don't fetch twice,

Local cache resolution

Stay ahead of the pipeline

Data engineeringintel, weekly.

Commonquestions.

Tell us whatto extract.We do the rest.

Related glossary terms

Edge Caching

Conditional GET (ETag)

Response Caching

Data Freshness