Show HN: Learn by rebuilding Redis, Git, a database from scratch

CodeCrafters is a free learning platform that teaches programming through hands-on projects where users build real systems from scratch—including Redis, Git, databases, and compilers—across 80+ courses in 9 languages. The platform offers structured learning paths for various career tracks (backend engineer, frontend engineer, DevOps, etc.) and uses a "choose → write → run" methodology to reinforce understanding through practical problem-solving rather than passive instruction.