PostHog is a comprehensive product analytics and customer data platform (CDP) built as a polyglot monorepo. It combines Python/Django for core application logic and API, Rust for high-performance event ingestion and symbolication, and Node.js for ingestion pipelines and CDP services. The frontend is a React/TypeScript application using Kea for state management. It supports self-hosting and cloud deployment, with data stored in PostgreSQL, ClickHouse, and Redis. Key features include event tracking, session replay, feature flags, experiments, error tracking, and AI observability. The architecture emphasizes high-throughput event processing via Kafka and Temporal workflows for async tasks.
Umami is a self-hosted, open-source web analytics platform that serves as a privacy-focused alternative to Google Analytics. The system tracks pageviews, sessions, events, funnels, journeys, retention, attribution, revenue, and performance metrics (Core Web Vitals) through a dual-database architecture using PostgreSQL (via Prisma ORM) and ClickHouse for analytics queries. It provides real-time dashboards, session replay, heatmaps, and a customizable board/dashboard system with shareable views. The application is built with Next.js (App Router) and React, using TypeScript throughout. It features a comprehensive REST API with auto-generated OpenAPI contracts, a generated TypeScript API client package, and an MCP (Model Context Protocol) server for AI/LLM integration. Authentication supports API keys, JWT, two-factor authentication (TOTP with backup codes), and team-based multi-tenancy with role-based permissions. Key architectural patterns include a dual-database query dispatcher (`runQuery`) that selects between Prisma and ClickHouse implementations for every analytics query, a centralized request parsing and validation layer using Zod schemas, and a hook-based React data layer with TanStack Query for caching and invalidation. The codebase also includes comprehensive test coverage with Vitest unit tests, Playwright API tests, and E2E tests, plus a coverage oracle that enforces every API endpoint is documented in the OpenAPI spec.