TinyKV

A minimal JSON-based key-value store for Rust with TTL support and multi-platform compatibility.

Overview

TinyKV provides a simple persistent key-value store that works across different Rust environments - from standard desktop applications to embedded systems and WebAssembly. Data is stored in human-readable JSON format with optional automatic expiration.

Features

• JSON file-based persistence with atomic writes
• TTL (time-to-live) expiration for keys
• Auto-save functionality
• Backup support with .bak files
• Multi-platform: std, no_std, and WebAssembly
• Flexible serialization: serde or nanoserde
• Thread-safe operations

Installation

Add to your Cargo.toml:

# Default configuration (std + serde)
tinykv = "0.4"

# For embedded systems (no_std + nanoserde)
tinykv = { version = "0.4", default-features = false, features = ["nanoserde"] }

# Minimal configuration (no_std only)
tinykv = { version = "0.4", default-features = false }

# WebAssembly support
tinykv = { version = "0.4", features = ["wasm", "nanoserde"] }

Quick Start

Basic Usage

use tinykv::TinyKV;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Create or open a store with namespace
    let mut store = TinyKV::open("data.json")?
        .with_auto_save()
        .with_namespace("app1");
    
    // Store some data (automatically prefixed with "app1:")
    store.set("username", "alice")?;
    store.set("count", 42)?;
    
    // Store with expiration (1 hour)
    store.set_with_ttl("session_token", "abc123", 3600)?;
    
    // Retrieve data
    let username: Option<String> = store.get("username")?;
    let count: Option<i32> = store.get("count")?;
    
    // List keys (returns ["username", "count", "session_token"])
    let keys = store.keys();
    
    println!("User: {:?}, Count: {:?}", username, count);
    Ok(())
}

Embedded Systems (no_std)

#![no_std]
extern crate alloc;
use tinykv::TinyKV;

fn main() -> Result<(), tinykv::TinyKVError> {
    let mut store = TinyKV::new();
    
    store.set("device_id", "ESP32_001")?;
    store.set("config", "production")?;
    
    // Serialize for external storage
    let serialized = store.to_data()?;
    
    // Later, restore from serialized data
    let restored_store = TinyKV::from_data(&serialized)?;
    
    Ok(())
}

WebAssembly

import { TinyKVWasm } from 'tinykv';

// Use browser localStorage
const store = TinyKVWasm.openLocalStorage('myapp');
store.set('theme', 'dark');
store.setWithTtl('session', 'abc123', 3600); // 1 hour

// Prefix operations
const userKeys = store.listKeys('user:');     // ['user:123', 'user:456']
const deleted = store.clearPrefix('temp:');   // returns count

Note: For optimal performance, serve WASM files with Content-Type: application/wasm. TinyKV will automatically fallback to slower instantiation if the MIME type is incorrect.

Data Format

TinyKV stores data in a structured JSON format:

{
  "username": {
    "value": "alice",
    "expires_at": null
  },
  "session_token": {
    "value": "abc123",
    "expires_at": 1725300000
  }
}

Feature Flags

• std (default): Enables file I/O, TTL, and standard library features
• serde (default): Uses serde for serialization (maximum compatibility)
• nanoserde: Uses nanoserde for faster compilation and smaller binaries
• wasm: Enables WebAssembly support with localStorage backend

API Reference

Core Methods

• TinyKV::open(path) - Open or create file-based store
• TinyKV::new() - Create in-memory store
• set(key, value) - Store a value
• set_with_ttl(key, value, seconds) - Store with expiration
• get(key) - Retrieve a value
• remove(key) - Delete a key
• contains_key(key) - Check if key exists
• keys() - List all keys
• list_keys(prefix) - List keys with prefix
• clear() - Remove all entries
• clear_prefix(prefix) - Remove entries with prefix
• save() - Manually save to disk

Configuration

• with_auto_save() - Enable automatic saving
• with_backup(enabled) - Enable/disable backup files
• with_namespace(prefix) - Set key namespace prefix
• purge_expired() - Remove expired entries

Platform Compatibility

Use Cases

Ideal for:

• Application configuration files
• Game save data
• CLI tool settings
• Test data persistence
• Embedded device configuration
• Browser-based applications
• Rapid prototyping

Not recommended for:

• High-performance databases
• Complex relational queries
• Concurrent multi-user access
• Large datasets (>100MB)

Documentation

Full API documentation is available at docs.rs/tinykv.

Changelog

Version 0.4.0

• BREAKING: WASM setWithTtl now accepts number instead of bigint
• Added namespace support with with_namespace(prefix) method
• Added prefix operations: list_keys(prefix) and clear_prefix(prefix)
• Enhanced WASM bindings with listKeys() and clearPrefix() methods
• Modernized package.json with exports field and sideEffects: false
• Improved WASM performance documentation

Version 0.3.0

• Enhanced no_std support
• Updated documentation and examples
• Improved JSON output formatting

Version 0.2.0

• Added nanoserde support for minimal binary size
• Improved compilation speed
• Enhanced embedded systems compatibility

Version 0.1.0

• Initial release
• Core key-value operations with TTL
• File-based JSON persistence
• Auto-save and backup support

License

MIT License