fast_kv

A Redis-compatible in-memory data store — same RESP wire protocol and client ecosystem, built to be a faster, leaner alternative to Redis for key-value workloads.

Status: Under active development. Core string commands, TTL/expiry, and eviction are implemented. Many Redis commands are still on the roadmap.

Why fast_kv?

Redis is the default choice for in-memory caching and session state, but it carries years of general-purpose complexity. fast_kv keeps what matters — RESP compatibility, familiar commands, TTL semantics — and strips away what you don't need for a focused key-value server.

Use any Redis client. Run the same commands you already know. Get a server written in Rust with a small surface area and room to optimize.

Current capabilities

Area	Status
TCP server	Working — async event loop (pollio), concurrent clients
RESP protocol	Encode/decode — simple strings, errors, integers, bulk strings, arrays, null
String commands	PING, ECHO, SET, GET, DEL
Expiry	EXPIRE, TTL, SET EX / SET PX, lazy + active expiry sweep
Eviction	Configurable policies (LRU, LFU, random) via MAX_KEYS + EVICTION_POLICY
Persistence / replication	Not yet

Requirements

• Rust (2024 edition)

Quick start

git clone <your-repo-url>
cd fast_kv
cargo run

The server listens on 0.0.0.0:9736 by default.

Configuration

Set environment variables before starting (or use a .env file via dotenvy):

Variable	Default	Description
HOST	0.0.0.0	Bind address
PORT	9736	Listen port
MAX_KEYS	1000	Maximum keys before eviction kicks in
EVICTION_POLICY	NoEviction	NoEviction, AllKeysLru, VolatileLru, AllKeysLfu, VolatileLfu, AllKeysRandom, VolatileRandom
EVICTION_SAMPLE_SIZE	20	Sample size for LRU/LFU eviction
CLEANUP_INTERVAL	1000	Active expiry sweep interval (ms)

Example:

HOST=127.0.0.1 PORT=6379 MAX_KEYS=10000 EVICTION_POLICY=AllKeysLru cargo run

Try it

# Plain text (decoder accepts simple strings)
nc localhost 9736
PING

# Or RESP array commands
redis-cli -p 9736 SET mykey hello
redis-cli -p 9736 GET mykey

Testing

fast_kv ships with a Redis compatibility test suite — cases ported from the official Redis test suite.

cargo test                  # unit + integration (fast)
cargo test -- --ignored     # include slow expiry tests

See tests/README.md for the full mapping to upstream Redis test files.

Project layout

src/
├── main.rs              # Entry point
├── lib.rs               # Library crate (used by integration tests)
├── config/              # Environment-based configuration
├── server/              # Async TCP server (pollio event loop)
├── core/
│   ├── resp.rs          # RESP encode/decode
│   ├── cmd.rs           # Parsed command representation
│   ├── eval.rs          # Command dispatch + in-memory store
│   └── processor.rs     # Request pipeline
└── logger.rs            # File or stdout logging
tests/                   # Redis compatibility integration tests

Roadmap

• More string commands (MGET, SETNX, INCR, …)
• Hash, list, and set data types
• PERSIST, PEXPIRE, PTTL
• Pipelining and partial-buffer reads
• Optional persistence (RDB/AOF)
• Replication

License

TBD