Apollo Server 4 is a lightweight, open-source GraphQL server that's compatible with any GraphQL client. It introduces the `@apollo/server` package, decoupling plugins and frameworks from the core of Apollo Server, offering a stable API for HTTP and serverless frameworks. This allows users to build Apollo Server integrations for their framework of choice. The new version also simplifies its package structure, reducing bundle size, and provides a TypeScript-first development experience with schema-first documentation. Additionally, it improves type safety by enabling the use of typescript-resolvers and ensures resolver types match schema types through static checks. With its release, Apollo Server 4 is now generally available for users to start building production-ready GraphQL APIs.