Content Delivery Network (CDN)
A Content Delivery Network (CDN) is a geographically distributed network of servers that caches and delivers web content — such as images, scripts, and static files — from a location physically close to each user, reducing latency and load…
Definition
A Content Delivery Network (CDN) is a geographically distributed network of servers that caches and delivers web content — such as images, scripts, and static files — from a location physically close to each user, reducing latency and load on the origin server.
Overview
Without a CDN, every request for a website's assets travels all the way to a single origin server, which might be thousands of miles from the requesting user, adding latency and putting all traffic load on one location. A CDN solves this by caching copies of static content — images, CSS, JavaScript, videos, and increasingly even dynamic content at the edge — across many points of presence (PoPs) around the world, so a user in Tokyo is served from a nearby Tokyo edge server rather than an origin server in Virginia. CDNs typically work by intercepting DNS-resolved requests and routing them to the nearest healthy edge location, checking whether a valid cached copy exists (a cache hit) or fetching a fresh copy from the origin server if not (a cache miss), then caching that response for a configured time-to-live before it's considered stale. Beyond raw speed, CDNs provide significant resilience and security benefits: they absorb traffic spikes and DDoS attacks by distributing load across many servers, and most major providers bundle SSL/TLS certificate management and web application firewall features directly into the service. CDNs are foundational infrastructure for essentially every high-traffic website today, and they matter directly for Core Web Vitals and SEO, since reduced latency translates directly into faster Largest Contentful Paint scores. Cloud providers offer CDN services as part of their broader platform (a topic covered in courses like AWS Core Services), alongside dedicated CDN vendors, and modern frameworks like Next.js are frequently deployed on platforms with CDN edge networks built in by default.
Key Features
- Geographically distributed edge servers (points of presence)
- Caches static and increasingly dynamic content close to users
- Reduces latency by serving from the nearest available edge location
- Absorbs traffic spikes and helps mitigate DDoS attacks
- Often bundles TLS/SSL certificate management and web application firewalls
- Configurable cache time-to-live (TTL) for content freshness
Use Cases
Frequently Asked Questions
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