A minimal file-backed key-value store for Rust with no_std support.

I was working on Tazı (named after the Turkish sighthound), a JS/TS test runner and Jest alternative, when I needed simple persistent storage for test configurations and app settings.

I tried existing solutions:

• sled felt like overkill for storing simple config
• pickledb looked good but seemed unmaintained
• Rolling my own JSON persistence was getting repetitive

So I built tinykv - the simple KV store I wish existed. Turns out other Rust developers had the same problem.

• JSON file storage (human-readable, git-friendly)
• Optional TTL (expiration) per key
• Auto-save and backup options
• Atomic writes (no corruption)
• Simple serde integration
• no_std support for embedded systems
• Works in WASM environments

• default: Uses serde for maximum compatibility
• std: Enables standard library features (file I/O, TTL)
• nanoserde: Uses nanoserde for smaller binaries and faster compilation

# Default (std + serde)
tinykv = "0.3"

# Embedded systems (no_std + nanoserde)
tinykv = { version = "0.3", default-features = false, features = ["nanoserde"] }

# Ultra-minimal (pure no_std)
tinykv = { version = "0.3", default-features = false }

use tinykv::TinyKV;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut kv = TinyKV::open("settings.json")?
        .with_auto_save();

    kv.set("theme", "dark")?;
    kv.set_with_ttl("session", "abc123", 3600)?; // 1 hour

    let theme: String = kv.get("theme")?.unwrap_or("light".to_string());
    println!("Using {} theme", theme);
    
    Ok(())
}

The file looks like this:

{
  "theme": {
    "value": "dark",
    "expires_at": null
  },
  "session": {
    "value": "abc123", 
    "expires_at": 1721234567
  }
}

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

fn embedded_main() -> Result<(), tinykv::TinyKVError> {
    let mut kv = TinyKV::new(); // In-memory store
    
    kv.set("device_id", "ESP32_001")?;
    kv.set("sample_rate", "1000")?;
    
    // Serialize to string for flash storage
    let data = kv.to_data()?;
    // flash_write(&data)?;
    
    // Load from serialized data
    let mut kv2 = TinyKV::from_data(&data)?;
    let device_id = kv2.get("device_id");
    
    Ok(())
}

Good for:

• CLI tool configuration
• Game save files
• Application settings
• Test data that needs persistence
• Prototyping without database setup
• Embedded systems and IoT devices
• WASM applications

Not for:

• High-performance applications
• Complex queries or relationships
• Multi-user concurrent access
• Large datasets

tinykv works across different environments:

• Desktop applications: Full features with file I/O, TTL, backups
• Embedded systems: Memory-efficient with nanoserde serialization
• WASM projects: Browser-compatible with minimal footprint
• IoT devices: Ultra-minimal string-based storage

https://docs.rs/tinykv

MIT License - see the full text in the repository.