PyRedis — A Redis Server Built from Scratch in Python

Ever wondered what happens between typing SET mykey "hello" and getting back OK? I did — so I built an entire Redis server from scratch to find out. PyRedis is a fully functional Redis server implementation written in Python. It speaks the real RESP (Redis Serialization Protocol) over raw TCP sockets, handles thousands of concurrent connections using a single-threaded asyncio event loop, and implements a rich set of Redis commands — all without depending on any Redis libraries.

What It Supports

• Strings with TTL expiration using monotonic clocks and lazy eviction
• Lists with blocking pops (BLPOP) that suspend the coroutine until data arrives
• Streams with auto-generated IDs and blocking reads (XREAD BLOCK) via cooperative async waiters
• Transactions (MULTI/EXEC/DISCARD) with per-connection command queuing and atomic execution
• Master-Replica Replication — a full implementation of the PSYNC handshake, RDB snapshot transfer, real-time write command propagation, offset tracking, and the WAIT command for synchronous replication acknowledgments using asyncio.Condition

Why I Built It

I use Redis daily but treated it as a black box. Building it forced me to solve problems that don’t appear in typical web development: parsing binary protocols byte by byte, coordinating distributed state across replicas, and designing clean abstractions for a system that needs to be extended with new commands over time.

How It’s Built

The architecture follows a clean layered design. A RESP parser and encoder handle serialization. A command handler dispatches to a registry of self-contained command modules (each Redis command is its own class). A pluggable storage layer manages typed values with TTL support. A replication module handles the master-replica lifecycle end to end. Everything is type-hinted, tested with pytest-asyncio, and designed to be read as much as run.

Tech

Python · asyncio · RESP Protocol · TCP Sockets · Distributed Systems · pytest GitHub