RoadRunner is a high-performance PHP application server and process manager written in Go. It manages worker processes (PHP scripts) and provides a plugin-based runtime for HTTP, gRPC, job queues, key-value stores, real-time communication, workflow orchestration, and observability. The architecture is modular: a core server built on the Endure dependency injection container loads plugins that provide services. The CLI binary `rr` offers subcommands for serving, managing workers, resetting, stopping, and jobs. Configuration is via YAML (`.rr.yaml`) with environment variable substitution and includes. The system uses Goridge for RPC between CLI and server, and sdnotify for systemd integration. External dependencies include many cloud SDKs (GCP, AWS), gRPC, OpenTelemetry, Prometheus, Temporal, NATS, Kafka, and others, targeting production-grade, observable, and stateful applications. The project is MIT-licensed and maintained by SpiralScout, with CI/CD for cross-platform builds (Linux, macOS, Windows, FreeBSD) and Docker images.