Glossary & Other

Key Definitions

Origin Server – this is defined as the original, authoritative source of content, holding the master copy of all files. A CDN’s primary job is to reduce the frequency of this server being accessed by the users. It is also referred to as the website’s homebase.

Points of Presence (PoP) – A Point of Presence (PoP) is defined as the physical data center of the CDN. Various PoPs of a CDN are distributed globally and have several edge servers responsible for caching and serving content locally to the nearby users.

Edge Server – An Edge Server is responsible for ensuring that the origin server is only accessed as a last resort. Edge servers are present in a clustered form inside a PoP across cities and region worldwide to ensure redundancy and load sharing. Each edge server maintains a local cache that includes a large storing pool of static assets, HTML pages, API responses, and software downloads.

Border Gateway Protocol (BGP) - The Border Gateway Protocol (BGP) is the central authority telling all Autonomous Systems (AS) where to send traffic so that when you are trying to access a website, you actually land on it.

Autonomous System (AS) - An Autonomous System (AS) are the key components that combine together to form the internet system. Internet is a collection of various independent networks owned by different ISPs, organizations, governments, and CDN providers. Each independent network is called an Autonomous System.

Domain Name System (DNS) - A Domain Name System (DNS) is what makes domain names understandable to the computer systems. It acts between you typing a website name on your web browser and your device understanding what that means. For instance, when you type www.google.com on your web browser, DNS translates it to an IP address (192.168.140.1) for the computer system to understand.

Transport Layer Security (TLS) Settings - Transport Layer Security (TLS) is what secures the communication between your web browser and the server you are trying to access. Ever noticed https:/ written at the start of a URL? TLS is what runs underneath.

APAC - APAC is an acronym to represent Asia Pacific (Covering East Asia, Southeast Asia, South Asia, Oceania, and Pacific Island). It is treated as a unit or a specific operational zone in CDN architecture because of the geographic scale, infrastructure diversity, regulatory fragmentation, and CDN coverage gaps.

DNS Management Overhead - DNS Management Overhead refers to the additional risk, complexity, and work accumulating as a result of adding more DNS records, subdomains, and configurations, especially when these records are spread across multiple services, CDN providers, or environments.

Immutable Assets - Hashed filenames (e.g., main.a3f92c.js, logo.7d1e44.png). These never change at a given URL. They are ideal candidates for aggressive caching and for routing to a secondary CDN.

Versioned but Mutable Assets - Files served at stable URLs where the content may change on deploy (e.g., app.js, styles.css). These need careful cache invalidation handling across both CDNs.

Dynamic-adjacent Assets - Personalized images, A/B test variants, geo-targeted assets. These are poor candidates for a secondary CDN unless you can enforce consistent routing logic.

Mann-Whitney U Test - A non-parametric statistical test that compares two independent groups to determine whether one tends to produce systematically higher or lower values than the other, without assuming the data follows a normal distribution. It works by ranking all observations from both groups combined and then assessing whether one group's ranks are consistently higher. This makes it well-suited for CDN latency data, which is typically right-skewed and non-normal.

Two-Proportion Z-Test - A statistical test used to determine whether there is a significant difference between two independent proportions. For instance, whether the error rate on CDN A differs meaningfully from the error rate on CDN B. It works by computing a Z-score that measures how far apart the two proportions are relative to the variability expected by chance. It assumes a sufficiently large sample size so that the sampling distribution approximates a normal curve.

Chi-Squared Test - A statistical test used to determine whether there is a significant association between two categorical variables — for example, whether cache hit or miss outcomes are distributed differently across two CDN variants. It works by comparing the observed frequency of each outcome against the frequency you would expect if there were no difference between the groups. It is appropriate when your data consists of counts or proportions across discrete categories rather than continuous measurements.

Brotli Compressed Response - A Brotli compressed response is an HTTP response where the content has been compressed using Google's Brotli algorithm (Content-Encoding: br) before being transmitted from the server or CDN to the client. It achieves 15–25% better compression than gzip on text-based assets like HTML, CSS, and JavaScript, resulting in smaller file sizes and faster load times. The browser signals Brotli support via the Accept-Encoding: br request header and decompresses the response transparently before rendering — meaning the compression and decompression process is entirely invisible to the application layer.