Dragonfly

Dragonfly is a Redis-compatible in-memory data store rewritten in C++ with a multi-threaded architecture. Redis runs on a single core, which is its fundamental bottleneck; Dragonfly uses every core on the box. Self-hosted under BSL-1.1, free for internal use.

The headline is throughput. Dragonfly claims up to 25x on multi-core machines, and even conservative real-world tests show several times the performance of Redis on the same hardware. It also uses less memory for the same data. Migration is genuinely drop-in: point your app at Dragonfly on the same port with the same commands, and most apps work without code changes.

Solo and small teams running Redis without performance pain have no reason to switch. Teams hitting Redis's single-core ceiling get a free upgrade by swapping the binary. If you'd rather not self-host, Dragonfly Cloud is the managed option, starting around $0.023/hr (roughly $17/mo for a basic instance).

The catch is the license. BSL-1.1 converts to Apache 2.0 after four years, but until then you can't offer Dragonfly as a competing managed service. For internal use that does not matter. The bigger gotcha is compatibility edges: some Lua scripting and module behavior differs from Redis, so test your actual workload before you move production onto it.