Shift8 DB Cache

Shift8 DB Cache is an analysis-first WordPress plugin for identifying expensive database queries and turning only the approved ones into precise cache rules.

The plugin is intentionally conservative:

• capture first, cache later
• admin-started analysis windows
• narrowly targeted query fingerprints
• Redis-backed active caching for approved fingerprints
• stale-once refresh behavior for opted-in rules

What it does

The current implementation supports two operating modes:

• analysis mode for capturing and ranking expensive SELECT fingerprints
• active caching mode for specific approved fingerprints backed by Redis

The plugin only caches read queries that match an approved normalized SQL fingerprint. Non-SELECT queries and SELECT ... FOR UPDATE are excluded from caching.

Installation

1. Copy the plugin folder into wp-content/plugins/.
2. Activate the plugin from the WordPress admin.
3. Open Shift8 > DB Cache.

Usage

1. Click Start capture.
2. Browse the site normally for a representative period.
3. Stop capture and review the analysis table.
4. Create cache rules from the highest-value fingerprints.
5. Configure Redis and enable active caching.

Redis configuration

Active caching uses Redis through the phpredis extension.

Configure the destination from Shift8 > DB Cache:

• Redis host: accepts local or remote Redis hosts
• Redis port
• Redis database
• Redis key prefix
• Default rule TTL

For secrets, do not store a Redis password in the database. Define it in wp-config.php or an environment variable instead:

define( 'SHIFT8_DBCACHE_REDIS_PASSWORD', 'your-redis-password' );

Optional runtime overrides are also supported:

define( 'SHIFT8_DBCACHE_REDIS_HOST', 'redis.example.com' );
define( 'SHIFT8_DBCACHE_REDIS_PORT', 6379 );
define( 'SHIFT8_DBCACHE_REDIS_DATABASE', 2 );
define( 'SHIFT8_DBCACHE_REDIS_PREFIX', 'shift8cache' );
define( 'SHIFT8_DBCACHE_REDIS_TIMEOUT', 1.0 );

If Redis is unavailable, the plugin falls back to uncached reads and surfaces an admin notice instead of failing closed on frontend requests.

Rule execution

Approved rules are stored in WordPress options and executed through a minimal db.php drop-in. The drop-in only wraps get_results(), get_row(), get_var(), and get_col() and only for approved SELECT fingerprints.

The plugin will not overwrite a pre-existing third-party wp-content/db.php drop-in. If one already exists, active caching remains disabled and the admin screen shows a conflict notice.

Security and design principles

• Require manage_options for all admin actions.
• Verify nonces before changing capture state or settings.
• Sanitize all settings input before persistence.
• Prefer the smallest possible cache scope.
• Keep the active interception layer minimal and limited to explicit approved rules.
• Keep Redis passwords out of normal option storage.
• Refuse to override another database drop-in.

Development notes

This repository now includes the analysis phase plus a first active-caching phase with explicit rule authoring, a guarded db.php drop-in, Redis connectivity checks, and test coverage for rule normalization and runtime helpers. The plugin still intentionally avoids broad auto-caching or a large collector framework.

Testing

The plugin ships with PHPUnit-oriented unit tests for settings sanitization, query aggregation, rule storage, runtime matching, and drop-in synchronization behavior. If your environment has phpunit installed, run:

phpunit --configuration phpunit.xml

Roadmap

• Phase 1: analysis-only capture and rule authoring
• Phase 2: Redis-backed rule execution with stale-once behavior
• Phase 3: operational visibility for hit rate, misses, refreshes, and safe fallback behavior
• Phase 4: targeted invalidation strategies for approved query scopes