---
title: "What is tiered caching? Cache hierarchies in CDNs explained — warmup.rocks Glossary"
description: "Tiered caching routes edge-PoP misses through upper-tier data centers before the origin. How Cloudflare Tiered Cache and similar hierarchies work, and what they change about warming and purging."
canonical: https://warmup.rocks/glossary/tiered-cache
---

# Tiered caching

**Tiered caching** arranges a CDN's data centers into a hierarchy: when an edge [PoP](https://warmup.rocks/glossary/point-of-presence) misses, it fetches from a designated upper-tier PoP instead of going straight to your origin. Only an upper-tier miss reaches the origin. Cloudflare's Tiered Cache is the best-known implementation; CloudFront's regional edge caches work the same way by default.

## Why CDNs build hierarchies

Hundreds of independent edge caches each fetching from one origin scales badly — for your server and for the visitor waiting on the miss. A hierarchy fixes both directions: upper tiers are fewer, bigger and hotter (they aggregate demand from many edge PoPs, so objects survive longer before [eviction](https://warmup.rocks/glossary/cache-eviction)), and the origin only ever talks to a handful of upper-tier locations. The single-tier special case is an [origin shield](https://warmup.rocks/glossary/origin-shield).

## What changes in the headers

A hit at the upper tier still reaches you as a miss-ish experience: with Cloudflare, the edge reports `cf-cache-status: MISS` while the response actually came from another colo's cache — faster than origin, slower than a local `HIT`. The [Age header](https://warmup.rocks/glossary/age-header) carries over from the tier that stored the object, which is why a "fresh miss" can arrive with a large Age. Diagnosing per-location behavior needs measurements from several regions — a [multi-location cache check](https://warmup.rocks/cache-checker) makes the tiers visible.

## Implications for purging and warming

-   **Purges must clear every tier** — modern CDN purges do, but third-party layers (reverse proxies, Varnish) in front of your origin form an ad-hoc tier that purges won't reach.
-   **Warming benefits compound:** one warming request through a cold edge PoP fills that PoP _and_ its upper tier — so subsequent misses at other edge PoPs under the same tier get a fast tier hit instead of an origin trip. [Our Cloudflare warming guide](https://warmup.rocks/blog/cloudflare-cache-warming) covers the interplay in detail.