Rebuild Classics: Learn by rebuilding Redis, Git and databases from scratch

What it does

Rebuild Classics is a programming education platform where learners build real systems from scratch. Rather than following tutorials, students write code for projects like Redis, Git, databases, kernels, and compilers. Each project breaks into graded lessons. A real executor runs the code against visible and hidden tests, and the artifact is a genuinely functional system—not a simulation.

The platform offers 80+ build-from-scratch courses across 37 language tracks. Examples include a Redis server that responds to real redis-cli commands, a Git implementation that git log can read, and a kernel that boots. Lessons progress from an empty file to a working system.

Who it is for

The platform targets developers who want to understand how core software works by implementing it themselves. The courses range from intermediate to advanced difficulty. Learners can use their own editor and repository; linking a GitHub repo means every push is graded automatically and progress updates a README badge.

Pricing

The site does not show pricing. It states that courses are free forever with no credit card required.

How it stands out

The core difference is automated, real-world grading. Hidden tests prevent solutions from merely appearing correct. The artifacts are genuinely usable—a Redis server that works with the actual redis-cli, not a mockup. Learners use their own development environment and tools, not a locked-in editor. Certificates are issued only when all graded exercises pass and can be publicly verified.

The breadth is unusual: 1,900+ graded exercises across systems as varied as neural networks, TLS 1.3, and containerization.

What a founder should check

A rival builder should verify three things. First, what happens to learner retention after the free tier—does a freemium conversion funnel exist, and at what percentage? Second, whether the hidden test infrastructure actually prevents cheating at scale, since the value proposition depends entirely on grading credibility. Third, how switching costs work: once a learner has invested weeks in a course and earned a certificate, what incentive keeps them on the platform for a second course, or do they have full portability to take the same course design elsewhere?

Thinking of building something like this?

Every launch here is a competitor to somebody's idea. If yours is close, check it against the market before you build: the Full Check names the rivals, the prices and the gaps.