Zedis

A Redis-compatible in-memory data store written in Zig, designed for learning and experimentation. Zedis implements the core Redis protocol and data structures with a focus on simplicity, performance, and thread safety.

Not intended for production use yet.

Features

• Redis Protocol Compatibility: Supports the Redis Serialization Protocol (RESP), including pipelined commands.
• Multiple Data Types: Strings and integers, lists, time series, and Bloom filters.
• Core Commands: Key management (DEL, EXISTS, TYPE, TTL, EXPIRE, KEYS), strings, lists (LPUSH/RPUSH/LRANGE, ...), and RANDOMKEY.
• High Performance: Written in Zig, with a single-executor command path and no global store lock.
• Key Expiration: Lazy TTL expiry on access, plus expiry checks during eviction.
• Disk persistence (RDB): Point-in-time snapshots of your dataset.
• Append-only file (AOF): Durable write-ahead logging with group commit.
• Memory Budgeting: Redis-compatible maxmemory with eviction, -OOM rejection for allocating commands, and cgroup-aware auto-sizing inside containers.
• Pub/Sub: Decoupled communication between services, with push delivery to idle subscribers.
• Time Series: Time series data structure. Now with Gorilla compression!
• Opinionated Design: No multiple logical databases, expiry is lazy only.

Caveats

• Zedis is intentionally single-store. It does not support multiple logical databases and does not expose Redis SELECT. It adds complexity and segment memory. This follows the reasoning Salvatore Sanfilippo gave when he called Redis multiple databases one of his worst design decisions.

Quick Start

Download the binary from the releases page or build from source to get started with Zedis.

Prerequisites

• Zig 0.17.0 (pinned in build.zig.zon)

Building and Running

# Clone the repository
git clone https://github.com/barddoo/zedis.git
cd zedis

# Build the project (optimized, ReleaseFast)
zig build --release=fast

# Run the server
zig build run --release=fast

The server will start on 127.0.0.1:6379 by default.

Testing with Redis CLI

You can test Zedis using the standard redis-cli or any Redis client:

# Connect to Zedis
redis-cli -h 127.0.0.1 -p 6379

# Try some commands
127.0.0.1:6379> SET mykey "Hello, Zedis!"
OK
127.0.0.1:6379> GET mykey
"Hello, Zedis!"
127.0.0.1:6379> INCR counter
(integer) 1
127.0.0.1:6379> TYPE mykey
string

Docker

Pre-built images are available on Docker Hub:

docker run -p 6379:6379 barddoo/zedis

Variants

Tag	Base	Notes	Use case
latest, x.x.x, x.x.x-debian, x.x.x-slim	Debian Trixie slim	Larger, glibc base	Default; broader ecosystem
x.x.x-alpine, alpine	Alpine 3.20	Smallest with shell	Size-sensitive deployments
x.x.x-distroless	Distroless static	No shell	Security-sensitive

Persistent data

Mount a volume to persist data across restarts:

docker run -p 6379:6379 -v zedis-data:/var/lib/zedis/data barddoo/zedis

Custom config

docker run -p 6379:6379 -v ./zedis.conf:/etc/zedis/zedis.conf barddoo/zedis

Development

Project Structure

The codebase is split by responsibility:

• src/app/ — server lifecycle, client connections, config, clock
• src/storage/ — store, KV allocator, lists, time series, Bloom filters, search
• src/commands/ — command handlers and registry
• src/persistence/ — AOF and RDB
• src/protocol/ — RESP parser and serializer
• src/util/ — mailbox, stack writer, types, compression
• src/benchmarks/ — micro/load benchmarks

See docs/server-architecture.md for the current server thread model and request flow.

Memory Management

See docs/memory-architecture.md for the current allocator layout, memory budgets, and runtime allocation behavior. See docs/store-cache-layout.md for the store's hash-table layout and cache behavior.

Building for Development

# Build in debug mode (default)
zig build

# Build optimized release (ReleaseFast; use this for benchmarks and performance testing)
zig build --release=fast

# `--release` with no mode also picks ReleaseFast (the preferred mode in build.zig)
zig build --release

# Run the full test suite
zig build test

# Run a focused subset
zig build test -Dtest-filter="Store"

# Format the source
zig fmt .

AI Disclaimer

This project was developed with some AI help. Most of the code was written by hand.

Contributing

Contributors are welcome! Whether you're fixing bugs, adding features, improving documentation, or suggesting enhancements, your contributions are appreciated.

Feel free to:

• Open an issue to report bugs or suggest features
• Submit pull requests with improvements
• Share feedback and ideas

Check out the open issues to see where you can help.

Stay Connected

• Subscribe to my newsletter

Thanks

• Andrew Kelley - For creating the amazing Zig Language.
• Redis - For the inspiration and protocol design.
• TigerBeetle - For the memory management and the tiger style.
• Karl Seguin - For the great articles.