How traffic actually finds and reaches a service, from DNS resolution through the protocols and infrastructure that sit in front of an application.
DNS translates human-readable domain names into the IP addresses computers actually use to route traffic, through a hierarchical lookup involving a recursive resolver, root name servers, TLD name servers, and finally the domain's own authoritative name server; caching at every layer of this chain is what keeps the process fast enough to be invisible in everyday use.
HTTP/2 fixed HTTP/1.1's head-of-line blocking problem by multiplexing many requests over a single connection; HTTP/3 went further by replacing the underlying transport protocol itself, moving from TCP to QUIC, to fix a deeper form of head-of-line blocking that persisted at the transport layer even after HTTP/2's fix.
An API gateway sits in front of a system's backend services as a single entry point, handling cross-cutting concerns like routing, authentication, rate limiting, and protocol translation centrally rather than duplicating that logic in every individual service; it earns its added latency and operational complexity specifically once an architecture has enough services that duplicating these concerns has itself become a problem.
A CDN caches and serves static content from locations close to users; edge computing extends the same 'close to the user' principle to actual computation, running application logic at distributed edge locations rather than only in a centralized region — useful specifically when a request needs real processing, not just a cached file, close to where it originates.