Artillery is a cloud-scale load testing and functional testing framework for backend services and APIs. It supports multiple protocols (HTTP, WebSocket, Socket.IO, Playwright, PostHog) through a plugin-based engine architecture. The system is primarily a CLI tool (built on oclif) that executes YAML/JSON test scripts defining virtual user flows with configurable arrival phases, payloads, and assertions. It provides distributed execution across local worker threads, AWS Lambda, AWS ECS/Fargate, and Azure ACI, with a bill-of-materials (BOM) system that bundles test dependencies for cloud workers. Metrics are aggregated via a custom Simple Statistics Measurement System (SSMS) supporting counters, histograms (DDSketch), and rates, and can be published to Datadog, CloudWatch, Prometheus, OpenTelemetry, Splunk, New Relic, and other observability platforms. The codebase is a monorepo managed with Turborepo, containing the core runner, platform integrations, first-party plugins (expect, ensure, apdex, slack, fake-data, metrics-by-endpoint, publish-metrics, memory-inspector), and shared type definitions. Key entry points include the `artillery` binary (`packages/artillery/bin/run`), the core runner (`packages/artillery/lib/core/runner.ts`), and platform launchers (`packages/artillery/lib/launch-platform.ts`). External dependencies include AWS SDK, Azure SDK, Playwright, got (HTTP client), and various metric publishing SDKs. The architecture is event-driven, using EventEmitter for lifecycle events and plugin hooks, with a global `global.artillery` object for shared state.