cpp-redis-clone: Redis-Inspired Key-Value Store

hussein hafez

Software Engineer

C++

Python

Computer Software

cpp-redis-clone

A high-performance, Redis-inspired in-memory key-value store written in modern C++ — demonstrating real-world systems engineering skills including protocol parsing, concurrency, durability, and observability. This project replicates the core functionality of Redis and is ideal for exploring custom data stores, embedded caches, or distributed job queues.

Features

RESP Protocol - Full implementation of Redis Serialization Protocol (RESP) with parser/serializer built from scratch

Thread-Safe Operations - Concurrent command processing with Boost.Asio and mutex-protected memory operations

AOF Persistence - Append-Only File logging with automatic replay on startup

TTL Support - Key expiration with background cleanup thread

Prometheus Metrics - Real-time monitoring of commands, memory usage, connections, and errors

Memory Tracking - Precise byte-level memory usage monitoring

Python Test Client - Integration testing with raw socket communication

Unit Testing - Comprehensive test suite using Google Test framework

Architecture

[Client] → [TCP Server Thread] → [RESP Parser] → [Command Handler] → [In-Memory Store]
                                                                    ↘ [AOF Log Writer]
                                                                    ↘ [Prometheus Metrics]

Each client connection runs in its own thread

TTL cleanup runs in background thread

All operations update metrics and AOF in real-time

Memory usage tracked at byte precision

Thread-safe command processing

Supported Commands

SET key value - Set key to hold string value

GET key - Get value of key

DEL key - Delete key

EXPIRE key seconds - Set key expiration time

TTL key - Get time to live for key

PERSIST key - Remove expiration from key

METRICS - Get Prometheus-compatible metrics

Quick Start

# Build
cd build
make

# Run
./redis-server

# Test
python3 test_client.py

# Run Unit Tests
./tests/resp_tests

Testing

Unit Tests

The project uses Google Test framework for comprehensive unit testing:

Store operations (SET, GET, DEL)

TTL and expiration handling

Memory usage tracking

Thread safety verification

AOF persistence

Example test output:

[==========] Running 8 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 8 tests from StoreTests
[ RUN      ] StoreTests.BasicOperations
[       OK ] StoreTests.BasicOperations (0 ms)
[ RUN      ] StoreTests.Expiry
[       OK ] StoreTests.Expiry (0 ms)
[ RUN      ] StoreTests.Persist
[       OK ] StoreTests.Persist (0 ms)
[ RUN      ] StoreTests.GetTTL
[       OK ] StoreTests.GetTTL (0 ms)
[----------] 8 tests from StoreTests (0 ms total)
[----------] Global test environment tear-down
[==========] 8 tests from 1 test suite ran. (0 ms total)
[  PASSED  ] 8 tests.

Integration Tests

The Python test client provides integration testing:

Full RESP protocol compliance

Command sequence verification

Metrics validation

Memory tracking accuracy

Metrics Example

redis_commands_total{command="set"} 1
redis_commands_total{command="get"} 2
redis_commands_total{command="del"} 1
redis_commands_total{command="persist"} 1
redis_commands_total{command="expire"} 1
redis_commands_total{command="ttl"} 1

redis_memory_bytes 120

redis_connections_active 1
redis_connections_total 10

redis_aof_writes_total 3
redis_aof_errors_total 0

Integration Test Output

Testing SET command...
Response: +OK

Testing GET command...
Response: $5
value

Testing EXPIRE command...
Response: :1

Testing TTL command...
Response: :9

Requirements

C++17

CMake 3.10+

Boost

Python 3

Google Test

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Posted Aug 16, 2025

Developed a Redis-inspired in-memory key-value store in C++.

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