Axii - High-Performance LSM-Based Key-Value Store

Axii is a high-performance, persistent key-value database implemented in Rust using a Log-Structured Merge Tree (LSM Tree) architecture. It is designed for high write throughput and scalability.

Architecture & Folder Structure

The project is organized as a Cargo workspace to ensure separation of concerns, scalability, and code reusability.

axii/
├── common/             # Shared library: custom errors, primitive types (Key, Value), and configs.
├── engine/             # Core library: LSM-Tree logic (Memtable, WAL, SSTables, Compaction).
│   ├── memtable/       # In-memory sorted structures (e.g., SkipList).
│   ├── wal/            # Write-Ahead Log for crash recovery and durability.
│   ├── sstable/        # Sorted String Table formats, indexing, and block management.
│   └── compaction/     # Background merge-sort logic for storage optimization.
├── server/             # Network binary: Handles TCP/gRPC client connections and queries.
├── cli/                # Terminal binary: Interactive REPL for database interaction.
└── tests/              # Integration tests covering cross-crate functionality.

Key Components

• Memtable: Fast in-memory writes using sorted structures.
• WAL (Write-Ahead Log): Ensures data durability before flushing to disk.
• SSTables: Immutable on-disk files for persistent storage with sparse indexing.
• Compaction: Background process that merges SSTables to reclaim space and optimize reads.

Getting Started

Prerequisites

• Rust (1.75+ recommended)

Build the Project

To build all crates in the workspace:

cargo build

Running the Components

Start the Server:

cargo run -p server

Launch the CLI:

cargo run -p cli

Running Tests

Run all unit and integration tests:

cargo test

Implementation Status

• Workspace & Crate Structure
• Common Type Definitions
• In-Memory Engine (Memtable)
• Write-Ahead Log (WAL)
• SSTables & Indexing
• Compaction Worker
• Network Server & CLI REPL