Content Delivery Network
A CDN answers requests from servers near the requester, trading a single origin for many cached edges.
A content delivery network is a distributed set of edge servers that cache and serve content close to the requester instead of routing every hit back to one origin. The win is latency — fewer network hops and less contention — and resilience, since the origin only has to handle cache misses and can survive a traffic spike that would otherwise flatten it directly.
Routing a request to the "nearest" edge is itself an interesting problem, and CDNs mostly solve it with Anycast or with Domain Name System tricks: the same IP address is announced from many locations, and normal internet routing (BGP) sends each client to whichever announcement is topologically closest, with no client-side logic involved. Some CDNs instead run DNS resolvers that return different edge IPs depending on where the query came from — geolocation by resolver, not by packet.
Caching introduces its own correctness problems. Static assets (images, JS bundles) are easy — hash the filename and cache forever. Anything personalized or frequently updated needs Cache Invalidation, which is famously one of the two hard problems in computer science. CDNs handle this with TTLs, purge APIs, and increasingly with edge compute — small pieces of application logic (auth checks, A/B routing, header rewriting) that run at the edge instead of the origin, blurring the line between "CDN" and "distributed platform."
The tradeoff CDNs make explicit is between consistency and locality: an edge node can serve a slightly stale copy fast, or fetch a fresh one slowly. That's the same tension Eventual Consistency names in distributed databases, just applied to HTTP responses instead of replicated state.
See also4
DNS over HTTPS
DNS over HTTPS wraps DNS lookups in encrypted HTTPS requests, hiding query contents from anyone but the resolver.
Networks & Distribution5 connections
Load Balancing
A load balancer spreads requests across many backend instances, turning "one server" into "one address."
Networks & Distribution15 connections
API Gateway
An API gateway is the single front door to a set of backend services, handling cross-cutting policy once instead of per-service.
Networks & Distribution9 connections
HTTP Caching
The set of headers that let a browser or intermediary reuse a previous response instead of re-fetching it.
Web Platform18 connections
Linked from19
- AnycastNetworks & Distribution
Anycast announces the same IP address from many locations and lets normal routing send each client to the nearest one.
- API GatewayNetworks & Distribution
An API gateway is the single front door to a set of backend services, handling cross-cutting policy once instead of per-service.
- BandwidthNetworks & Distribution
How much data a link can carry per second, why that's different from how fast it feels, and why a fast connection can still be slow for small requests.
- BitTorrentNetworks & Distribution
A peer-to-peer file-sharing protocol from 2001 in which everyone downloading a file also uploads pieces of it to others, so popular files get faster as more people want them, and its legitimate and pirate uses.
- Bloom FilterComputation & Algorithms
A probabilistic set membership structure that can say "definitely not present" but only "probably present."
- Consistent HashingComputation & Algorithms
A hashing scheme where adding or removing a node remaps only a small fraction of keys, not nearly all of them.
- Denial-of-Service AttackNetworks & Distribution
Making a service unavailable by overwhelming it with traffic or expensive requests, usually from many machines at once, and the layered defenses that absorb or filter the flood.
- DNS over HTTPSNetworks & Distribution
DNS over HTTPS wraps DNS lookups in encrypted HTTPS requests, hiding query contents from anyone but the resolver.
- FirewallNetworks & Distribution
A filter that allows or blocks network traffic by rule, the oldest perimeter defense, and less sufficient on its own than it used to be.
- HotlinkingWeb Platform
Displaying an image or file on your page straight from someone else's server, so they pay for the traffic, which sites block by checking where requests come from and which courts have treated differently from copying.
- HTTP CachingWeb Platform
The set of headers that let a browser or intermediary reuse a previous response instead of re-fetching it.
- HTTP Status CodeWeb Platform
The three-digit number at the start of every HTTP response that tells the client, caches, crawlers and monitoring what happened, grouped into five classes by the first digit.
- Load BalancingNetworks & Distribution
A load balancer spreads requests across many backend instances, turning "one server" into "one address."
- MIME TypeWeb Platform
The short type/subtype label, born in email, that tells a browser how to treat a response, and why browsers that guess when it's missing turned a convenience into a security hole.
- Object StorageData & Content
Storage that keeps whole files as objects addressed by key in a flat namespace over HTTP, cheap and nearly limitless, which became the foundation for backups, media, and data lakes.
- Responsive ImagesWeb Platform
Offering the browser several versions of an image so it can download the smallest one that still looks sharp on this screen at this layout size.
- Reverse ProxyNetworks & Distribution
A server that sits in front of other servers and receives clients' requests on their behalf, handling encryption, routing, caching, and protection in one place.
- Time to LiveNetworks & Distribution
A limit on how long something may live, counted in hops or seconds, which keeps lost packets from circling forever and tells caches when their copies go stale.
- Web HostingWeb Platform
Renting space on someone else's servers to put a website online, a business that moved from free personal pages and crowded shared machines to virtual servers, rented cloud infrastructure and services that host static files at the edge of the network.