How Cache Hit Ratio and Latency Turn Into Dollars

When you run a website or app, two ideas pop up again and again: cache hit ratio and latency. They sound technical, but they both lead straight to money—how much you pay to deliver data, and how much you earn when visitors stick around. This guide explains what they mean in plain terms, how they affect cost and revenue, and how you can put numbers to them.

Think of your main server as a warehouse. Every time someone requests a page or image, that data has to "leave the warehouse" to reach them. Your host often charges you for that—data going out is called egress, and it adds up. (We go deeper on why egress is often a "silent tax" in Cloud Egress Hidden Costs.) A cache is like a small copy desk closer to your visitors (for a plain-language intro to how caching works on the web, see HTTP Caching in Plain Language): instead of every request going all the way to the warehouse, many can be answered from the copy. When a request is answered from the copy, that's a cache hit. When it has to go to the warehouse, that's a cache miss.

Cache hit ratio (CHR) is simply: out of every 100 requests, how many were served from the cache? If 80 out of 100 are hits, your CHR is 80%. High CHR means less traffic hitting your main server—so less data "leaving the warehouse" and lower egress cost. Low CHR means most requests still go to the origin, so you pay for more data transfer.

Example: Suppose your site sends 1,000 GB of data out each month and your provider charges $0.09 per GB. That's $90. If you add a CDN and your cache hit ratio is 70%, only 300 GB comes from your origin; the rest is served from the edge. Your origin egress drops to 300 GB—about $27—so you save roughly $63 on bandwidth. The higher the CHR, the more you save.

Latency is how long it takes for the first piece of data to reach the visitor after they ask for a page—often called "time to first byte" (TTFB). Imagine a drive-through: if the window opens in two seconds, you wait. If it takes 10 seconds, some people drive away. On the web, studies show that when a site feels slower by about 100 milliseconds, a small but real slice of visitors leave or don't complete a purchase. So faster responses don't just feel better; they can mean more conversions and more revenue.

Serving from a cache (or a CDN or reverse proxy close to the user) usually reduces latency because the answer doesn't have to travel from one central server. A rule of thumb that's been around for a long time—it comes from Amazon's own A/B tests in the early 2000s, first shared publicly in 2006—says that for every 100 ms you improve that "time to first byte," you might recapture around 1% of conversion that would otherwise be lost. The data is old, but the idea is still widely cited because it makes the point clearly: latency isn't only a cost story—it's a revenue story too.

Example: Your app earns $50,000 per month. You improve TTFB by 200 ms (e.g. by using a CDN). If that 1%-per-100ms idea holds for you, that could mean about 2% more conversion—$1,000 extra per month. That's not guaranteed for every site, but it illustrates how speed can turn into dollars.

On the cost side, a higher cache hit ratio means less data leaving your main server, so your egress bill drops. On the revenue side, better latency can mean fewer people bouncing and more completing a signup or purchase. The trick is to turn those ideas into numbers so you can decide whether something like a CDN is worth the subscription fee.

To move from theory to reality, run your own baseline audit using the following frameworks: First, the API & Cloud Egress Cost Modeler lets you estimate how much you pay today for data transfer—based on users, requests, and file sizes. That gives you a baseline: "this is what egress costs me without a cache." Second, the CDN ROI & Savings Calculator lets you plug in your monthly traffic, cache hit ratio, and latency improvement, and see how much you could save on egress plus how much you might recapture in revenue from being faster. Subtract the CDN's monthly cost and you get a simple "does it pay for itself?" view.

Example: You run a small SaaS. The egress calculator says you're on track for $200/month in bandwidth. You consider a CDN that costs $50/month. You estimate a 70% cache hit ratio and a 150 ms latency improvement. The CDN ROI calculator might show $140 in egress savings and, say, $500 in revenue recapture (if your monthly revenue is high enough and the old-but-often-cited 1%-per-100ms idea applies). Total benefit $640, minus $50 for the CDN, leaves $590 net—so the CDN pays for itself many times over. Your numbers will differ, but the same logic applies: compare savings and revenue lift to the subscription cost.

Cache hit ratio and latency both answer: "How much of my traffic is handled the cheap, fast way?" When most requests are served from the edge (high CHR), you pay less for data leaving the origin and users often see a faster response. When latency drops, fewer people leave before the page loads, so you can recapture some of the revenue that would have been lost. Neither metric is just a vanity number—they connect directly to what you pay and what you earn. Use the egress calculator to see your current cost, then the CDN ROI calculator to see how CHR and latency improvement could change the picture.