Capability inventory

Features

QuantumCache accelerates WordPress with query caching and fragment caching inside PHP. Free covers public traffic and core operator controls. Pro adds WooCommerce-aware behavior, optional logged-in caching, observability, and CDN-aware purge workflows.

Shared by Free and Pro

Core Engine

Both tiers use the same underlying cache engine and store layer.

Query and fragment caching

QuantumCache caches WordPress query results and reusable HTML fragments instead of storing whole page responses. Shared fragment coverage includes post bodies, excerpts, query loops, navigation, latest-posts blocks, archive blocks, and classic sidebars. Pro extends that model with WooCommerce-specific fragments.

Store layer and invalidation

Redis is the primary store when available, with a built-in MySQL fallback. Cached entries are tagged so content changes can invalidate matching records. Shared hooks cover post updates, taxonomy changes, and selected WordPress option changes.

DIAG-003
Query cache and fragment cache — two internal layers
%% DIAG-003 — Query Cache vs Fragment Cache: Internal Relationship
%% Source: qc_source_of_truth.md §6 (Terminology: Query cache, Fragment cache), §1.9 (counter data)
%% Fragment hits consistently exceed query hits in count across all tested segments and configs.
%% Source files do not define the specific fragment boundaries.

flowchart LR
    PHP["PHP execution process"]

    subgraph QC_LAYERS["QuantumCache — Two Internal Cache Layers"]
        direction TB
        QCACHE["Query Cache\n─────────────────────────────────────\nStores results of database queries.\nHit = DB call skipped.\nMeasured: query_hits / query_misses"]
        FCACHE["Fragment Cache\n─────────────────────────────────────\nStores rendered HTML or data fragments.\nHit = rendering skipped.\nMeasured: frag_hits / frag_misses\n\nNote: fragment boundaries are not defined\nin source files"]
    end

    DB["Database"]
    RENDER["Rendering\n(fragment assembly)"]

    PHP -->|"check"| QCACHE
    QCACHE -->|"miss → query"| DB
    DB -->|"result"| QCACHE
    PHP -->|"check"| FCACHE
    FCACHE -->|"miss → render"| RENDER
    RENDER -->|"fragment stored"| FCACHE

    note1["Fragment hits are consistently higher in count than query hits\nacross all tested segments and configs (benchmark-derived, §1.9 — see TABLE-004)"]
    note2["Neither layer stores complete HTTP responses.\nQuantumCache is not a full-page cache."]

    style PHP fill:#f5f5f5,stroke:#aaa
    style QC_LAYERS fill:#f0fdf4,stroke:#16a34a
    style QCACHE fill:#dcfce7,stroke:#16a34a
    style FCACHE fill:#dcfce7,stroke:#16a34a
    style DB fill:#f5f5f5,stroke:#aaa
    style RENDER fill:#f5f5f5,stroke:#aaa
    style note1 fill:#f8f8f8,stroke:#ccc,color:#555
    style note2 fill:#fffbeb,stroke:#d97706,color:#92400e

QuantumCache stores query results and fragments inside WordPress execution. It is not a full-page cache.

Operational guardrails

  • Designed for front-end GET and HEAD traffic, not wp-admin, feeds, or search results.
  • Shared keys are scoped by site, locale, and cache context.
  • Fragments that contain nonce fields or JWT-like tokens are not stored.

Free and Pro share this same execution model. The difference between tiers is the extra policy, variation, WooCommerce, observability, and CDN behavior that Pro layers on top.

Tier

QuantumCache Free

Free is aimed at public, logged-out traffic and gives operators the controls needed to run and inspect the cache.

Public-site coverage

  • Caches anonymous front-end requests with the shared query and fragment engine.
  • Applies to standard WordPress pages across classic and block themes.
  • Includes automatic fragment coverage for post content, excerpts, query loops, navigation, archives, and sidebars.
  • Uses Redis when available and falls back to MySQL when Redis is unavailable.

WP-CLI and admin controls

  • wp quantumcache flush clears this site's cache entries.
  • wp quantumcache status reports backend, storage stats, and lifetime cache counters.
  • The admin page exposes store mode, Redis connection details, query TTLs, fragment TTLs, archive thresholds, auto fragments, debug headers, and debug markers.
  • Operators can purge everything, purge by tag, purge by URL, and inspect storage stats plus sample key and tag diagnostics.

WooCommerce in Free

WooCommerce catalog and product pages can still benefit when they behave like normal public content, but Free does not add WooCommerce-specific policy on top of the shared engine.

  • No WooCommerce-specific TTL overrides or session/cart bypass rules.
  • No product-specific invalidation map for stock, reviews, or order-driven catalog changes.
  • No logged-in role controls, Prometheus endpoint, or CDN tag-and-purge integrations.
Tier

QuantumCache Pro

Pro builds on Free and adds WooCommerce-aware controls and operational features for more complex stores.

Optional logged-in caching controls

  • Per-site toggle for logged-in caching, with a role allowlist and a separate TTL for approved users.
  • Logged-in cache approval is selective rather than blanket: admin, AJAX, REST, and sensitive account flows stay out of cache.
  • The same role-aware context is used by the shared query and fragment keys when logged-in caching is enabled.

WooCommerce-aware catalog behavior

Pro turns WooCommerce from “general public content” into a first-class cache policy surface.

  • Enables dedicated Woo capture for shop, product-category, and product-tag archives.
  • Applies a dedicated Woo archive TTL instead of treating the catalog like generic content.
  • Bypasses caching for cart, checkout, account routes, Woo AJAX, non-GET/HEAD requests, and Woo session or cart cookies.

Woo invalidation and key variation

Pro widens both the invalidation map and the cache key so Woo catalog pages stay safe when catalog state changes.

  • Purges product-related cache entries on product create, update, delete, stock changes, low-stock and no-stock events, reviews, relevant order activity, and catalog term changes.
  • Also purges on Woo settings that change catalog output, including currency, tax display, hide-out-of-stock behavior, and default customer address.
  • Extends Woo query variance for pagination, sorting, page size, search, min and max price, rating filters, layered-nav filter_* parameters, locale, currency, and geolocation hash when present.

Woo fragments, metrics, and CDN integrations

  • Adds dedicated Woo fragment coverage for breadcrumbs, result counts, sorting controls, archive product loops, related products, selected Woo widgets, and Woo blocks such as price and attribute filters.
  • Includes a Prometheus-compatible metrics endpoint with bearer-token protection, admin controls for viewing and resetting counters, and a wp quantumcache pro:metrics command.
  • Emits cache-tag and vary headers for downstream layers, plus provider-specific headers and purge integrations for Cloudflare, Fastly, and LiteSpeed.

What QuantumCache Is Not

Not a full-page cache

QuantumCache does not store or serve complete HTML responses. It stores query results and reusable fragments produced during WordPress execution.

Not a CDN

QuantumCache does not serve content from geographically distributed edge nodes. It operates at the origin server level, at the PHP/WordPress layer.

Not a replacement for page caching or edge layers

QuantumCache operates below a page cache and CDN in the request stack. Requests absorbed by those layers never reach QuantumCache. It complements them; it does not replace them.

See the rest of the picture

Architecture details, measured benchmarks, and the Free vs Pro comparison.

Benchmarks Free vs Pro comparison How It Works