Caching & Performance

Cache Layer Overview

Cache Layers

Layer	Technology	TTL	Scope	Purge Method
Browser	Cache-Control headers	Short (set by dezeen-cache-control plugin)	Per-user	Headers
CDN	Cloudflare	Varies by resource type	Global edge	Cloudflare API / dashboard
Page cache	Varnish	~1 day	Per-URL	Automatic on publish; manual via varnishadm
Application cache	WP Rocket	Until purge	Per-URL	WP Rocket admin; automatic on publish
Object cache	Redis (planned) / Transients	Varies	Per-key	wp cache flush; Redis FLUSHDB
ACF cache	ACF internal	Session	Per-request	ACF handles automatically

Cloudflare

Configuration

• Mode: Full CDN with WAF and DDoS protection
• DNS: Managed by Cloudflare
• Static assets: Cached at Cloudflare edge (CSS, JS, images, fonts)
• HTML: Passed through to Varnish (unless Cloudflare page rules cache it)

Purge

The dezeen-cloudflare-purge-manager plugin handles automatic cache purging:

• Purges homepage on post publish/update
• Fixes domain mapping issues (admin vs production URL)
• Logs purge operations for debugging
• Admin page: Settings → Cloudflare Purge Manager

Manual purge: Log into the Cloudflare dashboard → Caching → Purge Everything (or specific URLs).

Varnish

Configuration

• 2 Varnish servers in front of 4 Apache web nodes
• VCL files in setup/production/varnish/ (varnish-1-v8.vlc, varnish-2-v8.vlc)
• Health probes: /maintenance/ endpoint every 5 seconds

Monitoring

# Check backend health
varnishadm -T localhost:6082 -S /etc/varnish/secret "backend.list"

# Watch cache hits/misses
varnishlog -g raw -i Backend_health

# Validate VCL
setup/production/varnish/validate-vcl.sh

Purge

# Purge specific URL
varnishadm -T localhost:6082 -S /etc/varnish/secret "ban req.url ~ ^/some-path"

# Purge everything
varnishadm -T localhost:6082 -S /etc/varnish/secret "ban req.url ~ ."

WP Rocket

Setting	Value
Plugin version	3.20.3
Page caching	Enabled (WP_CACHE = true)
Debug mode	Controlled by WP_ROCKET_DEBUG constant
Cache busting	Fix applied via wp-rocket-cache-busting-fix.php mu-plugin

Known Issue

WP Rocket's cache-busting feature can throw E_WARNING errors when the cache/busting directory doesn't exist. The mu-plugin wp-rocket-cache-busting-fix.php suppresses these warnings.

dezeen-cache-control Plugin

Sets short browser TTL for HTML while keeping long shared-cache TTL for Varnish/Cloudflare:

Cache-Control: max-age=<short>, s-maxage=<long>

This ensures:

• Browsers get fresh content quickly
• Varnish/Cloudflare can serve stale content while revalidating

Hook: send_headers at priority 999 (runs last).

Image Optimisation

Tool	Purpose
WP Smush Pro (3.16.4)	Image compression, lazy loading, WebP conversion
smush-archive-guard.php	Prevents re-processing images uploaded before 2026-01-15
Theme lazy loading	Custom lazysize.js implementation
CDN	Images served via static.dezeen.com

Performance Optimisations in Theme

The theme's functions/performance.php implements:

Feature	Hook	Priority
CLS optimisation styles	wp_head	5
Preload critical resources	wp_head	1
Font display swap	wp_head	2
Ad container optimisation	wp_footer	5
CLS monitoring script	wp_footer	10
Conditional YouTube lite embed	wp_enqueue_scripts	15

dezeen-performance-optimiser Plugin

Optimises WordPress autoload settings:

• Prevents large options from being autoloaded
• Cache optimisation for frequently-accessed options
• Update check throttling to reduce external HTTP requests
• Admin page: Settings → Performance Optimiser

Known Performance Constraints

Issue	Impact	Mitigation
Heavy ACF usage	Slow cold-start queries	ACF_CACHE=true, database indexing
Many active plugins	High hook count, increased memory	WP_MEMORY_LIMIT=256M, memory_limit=1024M
Missing DB indexes	Slow meta queries	See setup/optimisations/db-indexes.txt
Large media library	Smush processing time	Archive guard prevents re-processing old images
Multiple Algolia plugins	Potential conflicts	Consolidation planned

Redis Object Cache

Setting	Value
Plugin	Redis Object Cache 2.7.0
Host	127.0.0.1
Port	6379
Database	0
Prefix	dezeen_acf_
Status	Uncertain — configured in wp-config but docs say "planned"

Debugging Cache Issues

Check Cloudflare Cache Status

curl -I https://www.dezeen.com/some-page/ | grep -i cf-cache-status
# HIT = served from Cloudflare edge
# MISS = fetched from origin
# DYNAMIC = not cacheable

Check Varnish Cache Status

curl -I https://www.dezeen.com/some-page/ | grep -i x-varnish
# Two numbers = cache HIT (first is current, second is original request)
# One number = cache MISS

Check WP Rocket

1. View page source — look for <!-- This website is like a Rocket --> comment at bottom
2. Check _project/_web/wp-content/cache/wp-rocket/ for cached files
3. Enable WP_ROCKET_DEBUG in wp-config for additional headers

Flush All Caches

# WP Rocket (if WP-CLI available)
wp rocket clean --confirm

# Redis
wp cache flush

# Varnish (from Varnish server)
varnishadm "ban req.url ~ ."

# Cloudflare (via dashboard or API)

See also: runbooks/cache-purge.md