Glossary/Redis
    Databases

    What is Redis?

    Redis is an open-source, in-memory data store used as a database, cache, message broker, and streaming engine, known for sub-millisecond response times.

    Last updated: February 2026

    Redis Explained

    Redis (Remote Dictionary Server) is an in-memory data structure store that serves as a database, cache, message broker, and streaming engine. Operating primarily in memory, Redis delivers sub-millisecond response times, making it perfect for use cases requiring extreme speed. Redis supports rich data structures including strings, hashes, lists, sets, sorted sets, bitmaps, and streams. At M3L Software, we use Redis extensively for caching (reducing database load by 80%+), session management, real-time leaderboards, rate limiting, and job queues with Celery. Redis is a critical component in our high-performance architectures, sitting between the application and database to dramatically improve response times.

    Key Features

    Sub-millisecond response times
    Rich data structures (lists, sets, sorted sets, hashes)
    Pub/Sub messaging capabilities
    Lua scripting for atomic operations
    Optional persistence (RDB, AOF)
    Cluster mode for horizontal scaling

    Common Use Cases

    1
    Application caching layer
    2
    Session management
    3
    Real-time analytics and leaderboards
    4
    Rate limiting and throttling
    5
    Job queue backend (Celery, RQ)
    6
    Pub/sub messaging

    Frequently Asked Questions

    Is Redis a database or a cache?

    Both. Redis started as a cache but evolved into a full database with persistence options. Most commonly it's used as a caching layer in front of a primary database like PostgreSQL, but it can also serve as a primary database for certain use cases.

    When should I use Redis?

    Use Redis when you need: fast caching (API responses, database queries), session storage, real-time features (leaderboards, counters), rate limiting, or job queue backends. If your app has slow database queries, Redis caching is usually the first optimization.

    Does Redis lose data on restart?

    By default, Redis has persistence options. RDB snapshots save data periodically, and AOF (Append Only File) logs every write operation. With proper configuration, Redis can recover data after restarts.

    Related Terms

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