Redis

★ 5/5 · Infrastructure/Database

Redis is an in-memory data store used as a database, cache, streaming engine, and message broker.

Pros

De facto industry standard for caching and real-time data operations
supports multiple data structures (strings, lists, sets, hashes, streams, HyperLogLog)
exceptional performance at scale
very active maintenance and community

In-memory storage fundamentally limits scalability compared to disk-based databases
requires planned persistence strategy (RDB/AOF)
clustering setup adds operational complexity
memory costs can grow significantly

Free, open source (BSD 3-Clause); Redis Cloud managed service starting at $8/month

Developers building high-performance applications requiring fast caching, sessions, pub/sub messaging, and real-time data operations.