mini-redis

A Redis clone built from scratch in C++, following the internals of how Redis actually works — TCP sockets, the RESP wire protocol, in-memory storage, key expiry, and an event-driven I/O loop.

Why I'm building this

I wanted to understand what happens below the API — how a server actually accepts connections, reads bytes off the wire, parses a protocol, and responds. This repo documents that learning process commit by commit.

Build roadmap

Part	What gets built	Status
1	TCP server — socket, bind, listen, accept	✅ Done
2	Read loop — recv(), raw RESP bytes visible	✅ Done
3	RESP parser — decode arrays, bulk strings	✅ Done
4	Commands — PING, ECHO	✅ Done
5	In-memory store — SET, GET, DEL	✅ Done
6	Key expiry — EX, PX, TTL	✅ Done
7	Concurrent clients — epoll event loop	✅ Done

How to build and run

g++ -o mini-redis server.cpp
./mini-redis

Then in a second terminal:

redis-cli ping     # should return PONG
redis-cli set name paritosh
redis-cli get name

Tech

• Language: C++
• OS: Linux (uses POSIX socket APIs)
• Tested on: Kali Linux

What I'm learning

• How TCP servers work at the syscall level (socket, bind, listen, accept, recv, send)
• The RESP (Redis Serialization Protocol) wire format
• How std::unordered_map backs a key-value store
• Non-blocking I/O with epoll
• How std::chrono enables TTL/expiry logic