CodeCrafters (YC S22)

CodeCrafters (YC S22) is a platform that provides advanced programming challenges focused on rebuilding complex software systems from the ground up. Developers choose from 11 different challenges including building their own Redis, Git, Docker, SQLite, HTTP server, shell, and other fundamental tools. Each challenge is broken into multiple stages that guide users through implementing increasingly complex functionality while learning about the underlying protocols and architecture.

The platform stands out by letting developers work entirely within their own development environment—using their preferred IDE, terminal, and tools rather than a constrained web editor. Users push their code via Git to receive automated feedback and test results within seconds. This approach provides the structure of guided learning while maintaining the flexibility of real-world development workflows.

CodeCrafters (YC S22) is particularly valuable for intermediate to advanced developers looking to deepen their understanding of systems programming, distributed systems, and database internals. It's used by engineers from companies like OpenAI, Google, and NVIDIA for professional development, by computer science students seeking practical experience beyond academic exercises, and by developers preparing for system design interviews or wanting to contribute to open-source projects.