pizzakv

🍕 PizzaKV

An in-memory key-value store written in Zig with Redis protocol compatibility and persistent storage.

Overview

PizzaKV is a concurrent key-value database that implements a subset of the Redis RESP (REdis Serialization Protocol), allowing it to work with Redis clients for supported commands. It also supports a simpler custom protocol (Pizzaria Protocol) using \r delimiters. Built from scratch in Zig.

Features

• Dual Protocol Support:
  • RESP (Redis Serialization Protocol) - subset implementation compatible with Redis clients
  • Pizzaria Protocol - simple \r-delimited custom protocol
• Persistent Storage: Append-only file (AOF) persistence with buffered writes
• Prefix Search: Built-in radix tree index for efficient prefix-based queries
• Thread-Safe: Concurrent operations using sharded hash tables and RwLocks
• Zero Dependencies: Pure Zig implementation with no external dependencies

Supported Commands

RESP Protocol (Redis-compatible)

• SET key value - Store a key-value pair
• GET key - Retrieve a value by key
• DEL key - Delete a key

Pizzaria Protocol (\r-delimited)

• write key|value - Write a key-value pair (key and value separated by |)
• read key - Read a value by key
• delete key - Delete a key
• keys - Get all keys (using radix tree)
• reads prefix - Get all values for keys matching a prefix
• status - Server status check

Architecture

Core Components

• Sharded Hash Table: 64 shards with 1,048,576 total buckets for parallel access
• Radix Tree Index: Fast prefix search and key enumeration
• Persistence Layer: 8MB write buffer with automatic flushing
• TCP Server: Async I/O with connection pooling

Concurrency Model

• Per-shard RwLocks: Allow concurrent reads within each shard
• Global tree mutex: Protects radix tree modifications
• Atomic connection tracking: For graceful shutdown

Building

# Build optimized binary
make build

# Clean build artifacts
make clean

Running

# Start server in Redis mode (RESP protocol, port 8085)
./pizzakv -redis

# Start server in Pizzaria mode (\r-delimited protocol, port 8085)
./pizzakv

# The server will create a .db file for persistence

Technical Details

Memory Management

• Arena allocators for hash table entries (per-shard)
• Arena allocator for radix tree nodes
• C allocator for temporary operations

Hash Function

• FNV-1a hash with bit mixing for uniform distribution
• Minimizes collisions across 1M buckets

Persistence Format

Simple append-only format:

OPCODE|key|value\r

• W|key|value\r - Write operation
• D|key|\r - Delete operation

Thread Safety

• Shard-level RwLocks for concurrent hash table access
• Global mutex for radix tree operations
• Atomic counters for connection tracking

Project Structure

pizzakv/
├── main.zig           # Server, connection handling
├── storage.zig        # Sharded hash table
├── index.zig          # Radix tree for prefix search
├── persistence.zig    # AOF persistence layer
├── hashing.zig        # Hash function
├── redis.zig          # RESP protocol parser
├── command.zig        # Command execution
├── socket.zig         # TCP socket operations
└── benchmark_*.sh     # Benchmark scripts

Notes

• This implements a subset of RESP, not the full Redis protocol
• RESP commands are limited to SET, GET, and DEL
• The Pizzaria protocol provides additional commands (prefix search)
• Built with Zig 0.15.1 using -O ReleaseFast optimization