Definition
Redis is an open-source, in-memory data store that keeps frequently accessed data in your server’s RAM rather than on disk. Because RAM is orders of magnitude faster than disk storage, Redis can read and write data in microseconds. It is most commonly used for caching (storing pre-computed results), managing user sessions, powering real-time features like live notifications, and handling background job queues. Despite being an in-memory store, Redis can persist data to disk so it survives server restarts.
Why It Matters
As web applications grow, database queries become a bottleneck. Every page load might require dozens of queries, and under heavy traffic the database struggles to keep up. Redis sits between your application and your database, serving the most frequently requested data from memory instead of hitting the database every time. This can reduce response times from hundreds of milliseconds to single-digit milliseconds. Redis is also essential for features that require near-instant data access, such as live dashboards, real-time chat, and rate limiting. Most modern web frameworks, including Laravel, have built-in Redis support.
Example
A project management SaaS has a dashboard that shows task counts, recent activity, and team availability. Each dashboard load originally triggered fifteen database queries, and under load the page took three seconds to render. After introducing Redis to cache the dashboard data with a thirty-second expiry, the page loads in under two hundred milliseconds. The database handles a fraction of the queries it did before, and the application feels significantly more responsive.