Appwrite is an open-source backend-as-a-service (BaaS) platform that provides a comprehensive set of APIs for authentication, databases, storage, serverless functions, messaging, realtime, and more. The codebase is a hybrid monolithic-microservice architecture: a central PHP application (using the Swoole coroutine-based HTTP server) handles REST, GraphQL, and WebSocket requests, while background workers (over 20 types) process asynchronous tasks such as email delivery, function execution, database migrations, and usage analytics. The platform supports multiple database backends (MariaDB, MongoDB, PostgreSQL, ClickHouse) and a variety of messaging providers (SMS, email, push). It is designed for multi-tenant deployments with per-project isolation, OAuth2 social login, and extensive API versioning. The repository also contains a large collection of reusable PHP packages (the Utopia framework) that provide caching, queueing, query building, DNS resolution, NATS messaging, HTTP client, PSR-7 implementation, and more. These packages are independently published and can be extracted for use in other projects.