Cachify - Redis-like In-Memory Key-Value Store

Cachify is a lightweight, multithreaded, Redis-inspired in-memory key-value store written in C++. It supports TTL-based key expiration, concurrent client access via a custom TCP server, and a simple text-based command protocol. Cachify is ideal for learning in-memory databases, caching layers, or building fast key-value storage solutions.

---

Project Structure

Cachify/
├── Makefile            # Build instructions
├── README.md           # Project overview
├── cachify_client      # TCP client executable
├── cachify_server      # TCP server executable
├── commands.txt        # List of supported commands
├── include/            # Header files
│   └── kv_store.h      # KVStore class declaration
└── src/                # Source code files
    ├── client.cpp      # Client implementation
    ├── server.cpp      # Server implementation
    └── kv_store.cpp    # KVStore class definition

---

Features

• In-memory key-value storage with thread-safe access

• TTL-based key expiration with a background cleaner thread

• Multithreaded TCP server allowing multiple clients to connect concurrently

• Simple text-based protocol:

  • SET key value [ttl_seconds]
  • GET key
  • DEL key
  • SIZE
  • PING
  • QUIT

• Flexible stripes for concurrent access (default: 128 stripes)

---

Build Instructions

1. Clone the Repository

git clone <repo-url>
cd cachify

2. Build the Project

make

This will generate two executables:

• cachify_server → The server
• cachify_client → The client

---

Running the Server

Start the server on a specific port (default: 6379):

./cachify_server 6379

• If no port is provided, it defaults to 6379.
• The server supports multiple concurrent clients using threads.

---

Connecting with the Client

Connect to the server using the client executable:

./cachify_client 127.0.0.1 6379

• Default host is 127.0.0.1 and default port is 6379 if not provided.
• You can now type commands interactively.

---

Supported Commands

• SET key value [ttl_seconds] – Set a key with an optional TTL (time-to-live in seconds)
• GET key – Retrieve the value of a key
• DEL key – Delete a key
• SIZE – Return the total number of keys
• PING – Check server connectivity (returns PONG)
• QUIT – Disconnect the client

---

Example Session

> SET myKey "Hello World" 60
+OK
> GET myKey
$11
Hello World
> SIZE
:1
> DEL myKey
+OK
> GET myKey
$-1
> QUIT

---

How Cachify Works Internally

• KVStore class:

  • Uses striped hash maps and mutexes for thread-safe storage.
  • Each key can optionally have a TTL (expiry time).
  • Expired keys are cleaned by a dedicated background cleaner thread.

• Server:

  • Listens on a TCP port and spawns a thread per client.
  • Processes simple text commands and sends structured responses.

• Client:

  • Connects to server and sends/receives text-based commands interactively.

---

License

This project is licensed under the MIT License.