Redis

Redis is an open-source, in-memory data structure store that serves as a database, cache, message broker, and streaming engine. In the hosting world, Redis is primarily deployed as an object cache and session store to dramatically improve the performance of dynamic websites and applications.

For WordPress hosting, Redis object caching eliminates redundant database queries by storing frequently accessed data in memory. A typical WordPress page load might trigger 50-200 database queries; with Redis caching enabled, most of those queries are served from memory in microseconds instead of milliseconds. This can reduce page generation time by 50-80% on database-heavy sites.

Beyond WordPress, Redis is used across virtually every web framework and CMS: Laravel, Django, Magento, Drupal, and more. It supports complex data structures including strings, hashes, lists, sets, sorted sets, bitmaps, and streams, making it versatile for many use cases beyond simple key-value caching.

Hosting providers typically offer Redis as a premium addon or include it in higher-tier plans. On shared hosting, per-account Redis instances run with memory limits (usually 256MB-1GB) to prevent any single account from consuming all server RAM. On VPS and dedicated servers, Redis can be configured with larger allocations.

Redis Sentinel provides high availability through automatic failover, and Redis Cluster enables horizontal scaling across multiple nodes. The persistence options (RDB snapshots and AOF logging) ensure data survives server restarts when needed.

The project was recently relicensed under a source-available model, which led to the Valkey fork. However, Redis remains the dominant deployment in production hosting environments.