# DragonflyDB — Modern In-Memory Datastore Replacing Redis

> DragonflyDB is a modern replacement for Redis and Memcached. Written in C++ with a multi-threaded, shared-nothing architecture that achieves 25x throughput improvement over Redis. Fully compatible with Redis and Memcached APIs.

## Install

Save in your project root:

## Quick Use

```bash
# Docker
docker run -d --name dragonfly -p 6379:6379 docker.dragonflydb.io/dragonflydb/dragonfly

# Connect via redis-cli (fully compatible)
redis-cli -p 6379
> SET hello world
> GET hello
> HSET user:1 name William email w@tokrepo.com
> HGETALL user:1
> LPUSH queue task1 task2
> RPOP queue
```

## Intro

DragonflyDB is a modern in-memory datastore designed as a drop-in replacement for Redis and Memcached. Built from scratch in C++ with a multi-threaded, shared-nothing architecture that uses all CPU cores efficiently. In benchmarks, Dragonfly achieves 25x the throughput of Redis on a single node while reducing memory usage by up to 40%.

- **Repo**: https://github.com/dragonflydb/dragonfly
- **Stars**: 30K+
- **Language**: C++
- **License**: BSL 1.1 (converts to Apache 2.0 after 4 years)

## What DragonflyDB Does

- **Redis compatible** — RESP protocol, most Redis commands
- **Memcached compatible** — text and binary protocols
- **Multi-threaded** — shared-nothing, scales across all cores
- **Memory efficient** — novel data structures use ~40% less RAM
- **Snapshots** — RDB-compatible persistence
- **Replication** — Redis-compatible replication protocol
- **Pub/Sub** — full pub/sub support
- **Lua scripting** — Redis Lua scripts work unchanged
- **Cluster mode** — emulated cluster for Redis cluster clients
- **ACL** — Redis-compatible ACL system

## Architecture

Shared-nothing multi-threaded design: each thread owns a slice of the keyspace. No global locks. Novel dashtable data structure replaces Redis dict for lower memory overhead and better cache locality. IO is handled via io_uring (Linux) for minimal syscall overhead.

## Self-Hosting

```yaml
version: "3"
services:
  dragonfly:
    image: docker.dragonflydb.io/dragonflydb/dragonfly
    ports: ["6379:6379"]
    volumes:
      - dragonfly-data:/data
    ulimits:
      memlock: -1
volumes:
  dragonfly-data:
```

## Key Features

- Redis + Memcached wire compatibility
- 25x throughput vs Redis (single instance)
- 40% less memory usage
- Multi-threaded (shared-nothing)
- RDB snapshot persistence
- Replication
- Lua scripting
- ACL security
- io_uring (Linux)
- Drop-in replacement

## Comparison

| Store | Threads | Protocol | Memory |
|---|---|---|---|
| DragonflyDB | Multi (shared-nothing) | Redis + Memcached | Best |
| Redis | Single | RESP | Good |
| Valkey | Single | RESP | Good (Redis fork) |
| KeyDB | Multi (shared) | RESP | Good |
| Garnet (MS) | Multi | RESP | Good |

## 常见问题 FAQ

**Q: 能直接替换 Redis 吗？**
A: 大部分场景可以。RESP 协议兼容，大部分 Redis 命令支持。少数高级 Redis 功能（Redis Modules、某些 cluster 边缘行为）不支持。

**Q: BSL 限制？**
A: 4 年后自动转 Apache 2.0。期间自用完全 OK，只是不能做托管 Dragonfly 服务与官方竞争。

**Q: 为什么这么快？**
A: 多线程 + 无锁 shared-nothing + io_uring + 紧凑数据结构（dashtable）。单机可以跑满一台 96 核服务器。

## 来源与致谢 Sources

- Docs: https://www.dragonflydb.io/docs
- GitHub: https://github.com/dragonflydb/dragonfly
- License: BSL 1.1

---
Source: https://tokrepo.com/en/workflows/290af6cf-3641-11f1-9bc6-00163e2b0d79
Author: AI Open Source