# ProxySQL — High-Performance MySQL Proxy with Query Routing

> ProxySQL is a high-performance proxy for MySQL and its forks that provides connection pooling, read/write splitting, query caching, and real-time reconfiguration without restarts.

## Install

Save in your project root:

# ProxySQL — High-Performance MySQL Proxy with Query Routing

## Quick Use
```bash
# Install on Debian/Ubuntu
apt-get install proxysql

# Start and connect to the admin interface
systemctl start proxysql
mysql -u admin -padmin -h 127.0.0.1 -P 6032

# Add a backend server
INSERT INTO mysql_servers (hostgroup_id, hostname, port) VALUES (1, 'db1.example.com', 3306);
LOAD MYSQL SERVERS TO RUNTIME;
SAVE MYSQL SERVERS TO DISK;
```

## Introduction
ProxySQL sits between your application and MySQL, acting as an intelligent traffic manager. It multiplexes thousands of application connections into a small pool of backend connections, routes reads to replicas, and caches frequent queries — all configurable at runtime without downtime.

## What ProxySQL Does
- Multiplexes application connections to reduce backend connection overhead
- Routes queries to different backend servers based on rules (read/write splitting)
- Caches query results in memory to offload repetitive reads
- Supports query rewriting, mirroring, and firewall-style blocking rules
- Allows runtime reconfiguration via a MySQL-compatible admin interface

## Architecture Overview
ProxySQL is written in C++ for maximum throughput. It uses a multi-threaded event-driven architecture with epoll. Configuration lives in an embedded SQLite database with three layers: disk, memory, and runtime. Changes flow from memory to runtime atomically. The query processor evaluates regex-based rules to decide routing, caching, and rewriting per query.

## Self-Hosting & Configuration
- Install via official packages for Debian, Ubuntu, CentOS, or Docker
- Admin interface listens on port 6032 (MySQL protocol) for runtime config changes
- Application traffic connects on port 6033 by default
- Define hostgroups for primary and replica servers, then create query rules for routing
- Monitor backend health with built-in ping, replication lag, and read-only checks

## Key Features
- Runtime reconfiguration with no restarts or connection drops
- Connection multiplexing reduces backend load from thousands of app connections
- Query-level routing rules with regex matching and digest-based classification
- Built-in query cache with TTL control per rule
- Supports MySQL, Percona Server, MariaDB, and MySQL Group Replication

## Comparison with Similar Tools
- **HAProxy** — general-purpose TCP/HTTP load balancer; ProxySQL understands MySQL protocol for smarter routing
- **MySQL Router** — official Oracle proxy for InnoDB Cluster; ProxySQL supports more backends and advanced query rules
- **MaxScale (MariaDB)** — similar feature set with BSL license; ProxySQL is fully open source under GPL
- **PgBouncer** — connection pooler for PostgreSQL; ProxySQL serves the same role for the MySQL ecosystem

## FAQ
**Q: Does ProxySQL add significant latency?**
A: Overhead is typically sub-millisecond. Connection multiplexing and caching often result in net performance gains.

**Q: Can I use it with MySQL Group Replication or Galera?**
A: Yes. ProxySQL has native support for monitoring group replication and Galera cluster status to route traffic correctly.

**Q: How do I handle failover?**
A: ProxySQL monitors backend health and automatically shuns unhealthy servers, rerouting traffic to available nodes.

**Q: Is the admin interface secure?**
A: Bind the admin port to localhost or a private network and change default credentials. TLS is supported for admin connections.

## Sources
- https://github.com/sysown/proxysql
- https://proxysql.com/documentation/

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Source: https://tokrepo.com/en/workflows/asset-30d07efe
Author: AI Open Source