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Redis

In-depth entry

by Redis Ltd. · Database · also known as Redis Open Source, Redis Community Edition, Redis Stack

In-memory key-value data store used as cache, message broker and database, with data structures, Pub/Sub, Streams and, since Redis 8, built-in JSON, search and time-series modules

LicenseRef-RSALv2 OR SSPL-1.0 OR AGPL-3.0-only licenseOpen sourceFreePaidEnterpriseUsage-basedSelf-hostedCloudSelf-hostable
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Link verified Nov 2, 2026

Overview

Redis is an in-memory data structure server developed by Redis Ltd. It stores strings, hashes, lists, sets, sorted sets, bitmaps, HyperLogLogs, geospatial indexes and Streams behind a simple command protocol, persists to disk through snapshots and an append-only file, and replicates to followers with Sentinel or Cluster for failover and sharding. Beyond caching, it is used for sessions, rate limiting, leaderboards, Pub/Sub messaging and as the backing store for job queues such as BullMQ; its Lua scripting and functions run logic server-side. Starting with Redis 8, the capabilities previously shipped as Redis Stack modules (JSON documents, query and search including vector similarity, time series and probabilistic structures) are part of Redis Open Source.

Licensing has changed several times. Versions through 7.2 were BSD-3-Clause; 7.4 to 7.8 were offered under RSALv2 or SSPLv1, which are not OSI-approved; and from Redis 8.0 the vendor's license page describes a tri-license allowing users to choose RSALv2, SSPLv1 or AGPLv3, restoring an OSI-approved option. The 2024 change prompted the Valkey fork under the Linux Foundation. Redis Ltd. also sells Redis Software (self-managed) and Redis Cloud, which are proprietary.

Redis is single-threaded for command execution, memory-bound by design, and durable only to the extent persistence is configured; large datasets or strict durability needs call for a disk-based database alongside it.

Editorial note on uncertainty. license_spdx is an expression for Redis Open Source 8.x; RSALv2 has no SPDX identifier and is written as LicenseRef-RSALv2. Earlier versions carry different licenses.

Capabilities

  • In-memory data structures: strings, hashes, lists, sets, sorted sets, Streams, geospatial and probabilistic types
  • Persistence through RDB snapshots and append-only files
  • Replication, Sentinel failover and Cluster sharding
  • Pub/Sub and Streams for messaging and consumer groups
  • Lua scripting and Redis Functions
  • JSON, query/search with vector similarity and time-series capabilities built in since Redis 8
  • Client libraries for every mainstream language and the redis-cli tool

Typical workflows

  1. Cache database queries and rendered fragments in front of PostgreSQL
  2. Run background job queues with BullMQ or similar libraries
  3. Store sessions and rate-limit counters for web applications
  4. Index embeddings for vector search alongside application data

Strengths

  • Very low latency for in-memory operations
  • Rich data structures beyond plain key-value
  • Ubiquitous client support and operational familiarity
  • AGPLv3 option restored as an open-source choice from Redis 8

Limitations

  • Dataset must fit in memory
  • Durability depends on persistence configuration and is weaker than disk-first databases
  • Single-threaded command execution limits per-instance CPU scaling
  • License history complicates compliance review across versions

Prerequisites

  • Linux or macOS host, or a container; Windows via WSL or third-party builds

Who it is for

  • Backend developers
  • Platform engineers running caches and queues
  • Teams adding vector or JSON features without another store

Alternatives & comparison

NATS and RabbitMQ are dedicated message brokers with delivery guarantees and routing that Redis Pub/Sub and Streams only partly match; BullMQ is a queue library that runs on Redis rather than replacing it. PostgreSQL can serve as cache, queue (with pg-boss) and JSON store for smaller loads with full durability, and MongoDB overlaps with Redis' JSON document features while remaining disk-based.

  • Apache Kafka

    Distributed event streaming platform with durable, partitioned, replayable logs, Kafka Connect connectors and Kafka Streams processing

    Open sourceOpen source
  • BullMQ

    Redis-backed job and message queue for Node.js (with a Python port) offering workers, flows, rate limiting, repeatable jobs and a commercial Pro tier

    MixedOpen source
  • MongoDB

    Document database storing BSON documents with a rich aggregation pipeline, available as a source-available Community Server or the managed Atlas service

    Source-availableFree
  • NATS

    Lightweight Go messaging system with core pub/sub and request-reply plus JetStream persistence, key-value and object stores; a CNCF project

    Open sourceOpen source
  • pg-boss

    Node.js job queue that uses PostgreSQL tables and SKIP LOCKED for reliable background jobs, scheduling and retries without a separate broker

    Open sourceOpen source
  • PostgreSQL

    Open-source object-relational database server with a large extension ecosystem (PostGIS, pgvector, TimescaleDB) and broad SQL coverage

    Open sourceOpen source
  • RabbitMQ

    Open-source message broker in Erlang supporting AMQP 0-9-1 and 1.0, MQTT, STOMP and Streams, with routing, acknowledgements and quorum queues

    Open sourceOpen source
Compare Redis with its alternatives →

Sources & verification

Primary sources consulted for this record. Claims are tied to the fields each source supports; the automated link checker re-verifies every URL on a schedule.

  • License
    redis/redis LICENSE.txt

    https://github.com/redis/redis/blob/unstable/LICENSE.txt

    Supports: license_spdx

    checked Nov 1, 2026
  • License
    Redis Licenses

    https://redis.io/legal/licenses

    Supports: license_spdx, source_model, description

    Page states Redis 7.2 and earlier are BSD-3-Clause, 7.4–7.8 RSALv2 or SSPLv1, and 8.0 onward RSALv2, SSPLv1 or AGPLv3; Redis Software and Redis Cloud are closed source.

    checked Nov 1, 2026
  • Official documentation
    Redis Documentation

    https://redis.io/docs/latest

    Supports: capabilities, workflows, data_formats

    checked Nov 1, 2026
  • Official site
    Redis

    https://redis.io/

    Supports: name, summary, vendor

    checked Nov 1, 2026
  • Pricing page
    Redis Pricing

    https://redis.io/pricing

    Supports: pricing_model

    checked Nov 1, 2026
Confidence
High
Reviewed
Nov 1, 2026
Links
Verified · Nov 2, 2026

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