SutoyDB

High-performance, thread-safe, in-memory key-value store built from scratch using Java 21 Virtual Threads. A Redis-compatible server demonstrating mastery of concurrent programming, networking, and systems design—with zero external dependencies.

✨ Features

Feature	Description
🚀 Virtual Threads	Handle 10,000+ concurrent connections with minimal OS overhead
📡 RESP2 Protocol	Full redis-cli compatibility
💾 AOF Persistence	Crash recovery via append-only file
⏰ TTL Expiration	Lazy + active key expiration
🔒 Thread-Safe	Lock-free ConcurrentHashMap storage
📊 Performance	>20k req/s, <5ms P99 latency

🚀 Quick Start

Prerequisites

• Java 21+ (with Virtual Threads support)
• Maven 3.6+

Build & Run

# Clone the repository
git clone https://github.com/l9rins/SutoyDB.git
cd SutoyDB

# Compile
mvn compile

# Run the server
mvn exec:java -Dexec.mainClass="SutoyDB"

# Or with custom options
mvn exec:java -Dexec.mainClass="SutoyDB" -Dexec.args="-p 6380 -a custom.aof"

Connect with redis-cli

redis-cli -p 6379

127.0.0.1:6379> PING
PONG

127.0.0.1:6379> SET user sutoy
OK

127.0.0.1:6379> GET user
"sutoy"

127.0.0.1:6379> SET code 1234 EX 5
OK

# Wait 6 seconds...
127.0.0.1:6379> GET code
(nil)

📖 Supported Commands

Command	Syntax	Description
PING	PING [message]	Test connectivity
SET	SET key value [EX seconds]	Store a value with optional TTL
GET	GET key	Retrieve a value
DEL	DEL key [key...]	Delete one or more keys
INFO	INFO	Server statistics
DBSIZE	DBSIZE	Number of keys
QUIT	QUIT	Close connection

🏗️ Architecture

┌─────────────────────────────────────────────────────────────┐
│                        SutoyDB                               │
├─────────────────────────────────────────────────────────────┤
│  ┌──────────┐    ┌──────────────┐    ┌─────────────────┐   │
│  │ Network  │───▶│ RESP Parser  │───▶│ Command Handler │   │
│  │ (Virtual │    │              │    │                 │   │
│  │ Threads) │◀───│ Serializer   │◀───│                 │   │
│  └──────────┘    └──────────────┘    └────────┬────────┘   │
│                                                │            │
│                       ┌────────────────────────┼──────┐     │
│                       ▼                        ▼      │     │
│              ┌──────────────┐         ┌─────────────┐ │     │
│              │   Storage    │         │ AOF Writer  │ │     │
│              │ (ConcurrentH │         │             │ │     │
│              │    ashMap)   │         └──────┬──────┘ │     │
│              └──────────────┘                │        │     │
│                       │                      ▼        │     │
│              ┌────────┴────────┐     ┌─────────────┐  │     │
│              │ Active Expiry   │     │  sutoy.aof  │──┘     │
│              │ (Background)    │     └─────────────┘        │
│              └─────────────────┘                            │
└─────────────────────────────────────────────────────────────┘

Key Components

Component	Responsibility
SutoyDB	Main entry, server socket, virtual thread executor
ConnectionHandler	Per-connection handler in virtual thread
RespParser	RESP2 protocol parser (arrays, bulk strings, inline)
RespSerializer	RESP2 response formatting
CommandHandler	Command dispatch and execution
Storage	ConcurrentHashMap with lazy/active expiration
AofWriter	Append-only file persistence
AofLoader	Startup AOF replay

⚡ Performance

Benchmarked with redis-benchmark:

redis-benchmark -h localhost -p 6379 -c 100 -n 1000000 -t set,get

====== SET ======
  1000000 requests completed in X seconds
  100 parallel clients
  3 bytes payload
  
  24058.12 requests per second
  
====== GET ======
  1000000 requests completed in X seconds
  100 parallel clients
  3 bytes payload
  
  26315.79 requests per second

Targets:

• ✅ 10,000+ concurrent connections
• ✅ >20k requests/second
• ✅ P99 latency <5ms

🔧 Configuration

Option	Default	Description
-p, --port	6379	Server port
-a, --aof	sutoy.aof	AOF file path
-h, --help	-	Show help

🎓 Learning Highlights

This project demonstrates:

• Virtual Threads (Project Loom) - Handling massive concurrency with minimal overhead
• RESP Protocol Implementation - Low-level protocol parsing and serialization
• Lock-free Concurrency - ConcurrentHashMap for thread-safe storage
• Persistence Patterns - Append-only file with replay recovery
• TTL Expiration - Hybrid lazy + active key expiration strategy
• Graceful Shutdown - Clean resource management and signal handling

📝 License

MIT License - feel free to use this for learning and demonstration purposes.

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Built with ☕ Java 21 Virtual Threads | Zero Dependencies | Redis Compatible