"Entropy is inevitable. Data loss is not."

Chronos is a persistent, concurrent, and high-performance Key-Value store built from scratch in Rust. It implements a Log-Structured Merge-Tree (LSM) architecture similar to RocksDB or LevelDB, coupled with a custom TCP Protocol for remote access.

Designed as an educational deep-dive into systems engineering, Chronos bridges the gap between simple in-memory hashmaps and production-grade databases like Redis.

• Hybrid Storage Engine: Uses an in-memory MemTable (HashMap) for nanosecond-latency reads and disk-based SSTables for long-term storage.
• Write-Ahead Log (WAL): Guarantees Durability (ACID). Every write is appended to a log file before acknowledgement. If the server crashes, Chronos replays the WAL upon restart to restore the state (0% Data Loss).
• Tombstone Deletion: High-efficiency DEL command implementation that uses memory tombstones to mark records as deleted without triggering expensive disk re-writes.

• Multithreaded Server: Handles concurrent TCP connections using thread spawning and safe memory sharing.
• Lock-Free Reads: Implements Arc<RwLock<T>> to allow multiple simultaneous readers without blocking. Writers only block when absolutely necessary.
• Graceful Shutdown: Intercepts SIGINT (Ctrl+C) signals to safely block new connections, flush memory buffers to disk, and close TCP sockets without data corruption.

• Crash Recovery: Automatic "Rehydration" mechanism restores database state from disk on boot.
• Live Compaction: In-memory garbage collection to prune tombstones and duplicated logs, optimizing the read path.

The system is composed of three distinct layers, completely decoupled:

1. The Interface (Network Layer - server.rs): Raw TCP Sockets and Multithreading.
2. The Parser (Translation Layer - parser.rs): Zero-copy parsing transforming raw bytes into strict Command Enums.
3. The Core (Storage Layer - engine.rs): Volatile RAM storage and Append-only persistence file (chronos.db).

git clone [https://github.com/baltasarblanco/chronos_lsm.git](https://github.com/baltasarblanco/chronos_lsm.git)
cd chronos_lsm

cargo run

Expected Output:

🚀 CHRONOS SERVER LISTO Y ESCUCHANDO EN TCP 127.0.0.1:8080

Chronos includes its own built-in terminal client (similar to redis-cli). Open a second terminal and run:

cargo run --bin client

chronos> SET user:101 {"name": "Venom", "role": "Symbiote"}
OK
chronos> GET user:101
{"name": "Venom", "role": "Symbiote"}
chronos> DEL user:101
OK_DELETED
chronos> COMPACT
OK_COMPACTED

Tests performed on local hardware via a single sequential TCP connection. Measured using 10,000 consecutive operations.

(Note: These metrics reflect raw sequential round-trips. Concurrent throughput via thread-pooling is significantly higher).

Baltasar Blanco - Systems Engineer / Rustacean Building infrastructure from the atom up.