Serving from close to the user.
WHAT THEY ARE
Distributed networks of servers holding copies of content, close to users.
WHAT THEY PROVIDE
Lower latency, since the path is shorter Reduced load on the origin Absorption of traffic spikes and attacks Frequently, optimisation and security features
HOW USERS REACH THE NEAREST LOCATION
Naming-based direction, returning a different address by location Anycast, with routing selecting the location
WHAT AN EDGE LOCATION HOLDS
Cached copies of content, fetched from the origin on first request.
WHAT A CACHE MISS IS
A request for content not held, requiring a fetch from the origin.
WHY HIT RATE MATTERS
A low hit rate means most requests still reach the origin, and the benefit is limited.
WHAT REDUCES HIT RATE
Content marked uncacheable Query strings treated as distinct Cookies preventing caching Too many variants
WHAT TO CACHE
Static assets, aggressively Pages, where they are not personalised
WHAT NOT TO CACHE
Personalised responses, in a shared cache.
WHAT TO VERIFY
The hit rate, and what is missing.
