HTML caching vs Aggressive HTML caching in Adobe Experience Manager (AEM)

Hi ​@nsvsrk ,

In AEM, these are informal patterns, not product switches:

• “HTML caching”: Usually means normal caching of page HTML at Dispatcher (and often CDN) with moderate TTLs and regular invalidation on content publish. Priority: freshness, cache is a helper.
• “Aggressive HTML caching”: Means caching almost all HTML for as long as safely possible at browser + CDN + Dispatcher, with longer TTLs, stale-while-revalidate‑style behaviour, and a more complex invalidation strategy. Priority: max cache‑hit ratio and origin protection, accepting brief staleness.
• AEM On‑Prem vs AEMCS: Same idea in both: just different places you configure (your own CDN/Dispatcher vs Adobe‑managed CDN + Cloud Manager dispatcher). The distinction is about policy (TTL + invalidation), not a special AEM feature.

Dispatcher vs CDN usage

• Both patterns can use Dispatcher and CDN.
• Difference is how far you push them:
  • Standard HTML caching: Dispatcher + CDN with conservative TTLs; cache is a helper.
  • Aggressive HTML caching: Dispatcher + CDN tuned as primary protection layer (high cache-hit ratio, long TTLs, stale serving), with origin sized for misses and authoring activity.

1. “HTML caching” (standard)

Typical setup:

• Layers
  • Browser: modest Cache-Control (e.g. seconds–minutes).
  • Dispatcher: HTML cached on disk; invalidated by replication/flush, .stat files, or basic TTL.
  • CDN (if any): Medium TTL (e.g. a few minutes) so changes appear quickly.
• Config levers (examples)
  • Dispatcher /cache rules and .statfileslevel for page invalidation
  • Moderate Cache-Control / Surrogate-Control on HTML, aligned with AEM’s normal invalidation model
  • No or limited caching for highly dynamic / personalised pages

2. “Aggressive HTML caching”

Same stack, but with much more opinionated settings:

• Layers
  • Browser: HTML allowed to stay cached longer (within business tolerance).
  • Dispatcher: cache “almost everything”; may use TTL-based invalidation (e.g. ACS Dispatcher TTL) instead of flushing on every activation
  • CDN: longer TTLs (minutes–hours), often with stale-while-revalidate and stale-if-error, to keep serving cached HTML even while origin is refreshing or under load.
• Config levers (examples)
  • Aggressive Cache-Control for HTML: e.g. max-age=300,s-maxage=43200,stale-while-revalidate=43200,stale-if-error=43200 for public pages (exact values vary).
  • Dispatcher configured to cache almost all .html (and often JSON) and to ignore non‑functional query params (/ignoreUrlParams) so marketing parameters don’t explode the cache
  • For personalisation, use fragment techniques (SDI, client-side rendering, or permission-sensitive caching) so most of the page stays cacheable, and only small bits are dynamic.