| Product | Redis |
| Website | redis.io |
| Category | Database / Cache |
| License | RSALv2 / SSPLv1 (dual license since v7.4) |
| Pricing | Self-hosted (free), Redis Cloud (managed) |
What Is Redis?
Redis is an in-memory data structure store. It holds data in RAM for sub-millisecond read and write latency. Originally a caching layer, Redis has grown into a versatile data platform: caching, session management, message queues (Redis Streams), pub/sub, rate limiting, leaderboards, and real-time analytics. Most web applications use Redis somewhere in their stack.
Redis supports rich data structures: strings, hashes, lists, sets, sorted sets, bitmaps, HyperLogLogs, streams, and geospatial indexes. This means Redis isn’t just a key-value store — you can model complex data access patterns directly in Redis instead of building them in application code.
Key Features
Sub-Millisecond Latency
Data lives in RAM. Read and write operations complete in microseconds. When your application needs to respond quickly — page loads, API responses, real-time features — Redis is the layer that makes it possible.
Data Structures
Sorted sets for leaderboards, streams for event processing, hashes for user sessions, lists for queues, sets for unique visitors, geospatial indexes for location queries. Each data structure has O(1) or O(log N) operations built in.
Persistence Options
Redis can persist data to disk with RDB snapshots or AOF (Append-Only File) logging. RDB is point-in-time snapshots; AOF logs every write. Combine both for durability with fast recovery. Or run Redis as a pure cache with no persistence.
Redis Cluster
Scale horizontally with Redis Cluster. Data is automatically sharded across nodes, with built-in replication and automatic failover. Redis Cluster handles the scaling that a single Redis instance can’t.
Who Is This For?
- Any web application that needs caching (session, page, API)
- Real-time features (chat, notifications, live dashboards)
- Queue and job processing (Sidekiq, BullMQ, Celery)
- Rate limiting and throttling
Pros
- Sub-millisecond latency
- Rich data structures beyond key-value
- Proven at massive scale
- Huge ecosystem (every language, every framework)
- Redis Streams for event processing
- Pub/sub for real-time features
Cons
- License change (RSALv2/SSPLv1) from v7.4
- Data must fit in RAM (cost at scale)
- Single-threaded command processing
- Cluster adds operational complexity
- Forks: Valkey, KeyDB (community fragmentation)
Verdict
Redis is infrastructure that most applications need. Caching, sessions, queues, rate limiting, pub/sub — these are common requirements, and Redis handles all of them with sub-millisecond performance. The rich data structure support means you model your access patterns in Redis instead of building them in application code.
The license change (RSALv2/SSPLv1 since v7.4) is the main concern. It restricts cloud providers from offering Redis as a service, which led to the Valkey fork (Linux Foundation). For self-hosted use and development, the license is permissive. For cloud-managed Redis, evaluate Redis Cloud vs. Valkey-based alternatives.
Build a database or infrastructure tool?
Get reviewed and linked from our 27-site network.
See Packages