Replit has been utilizing Nix to provide consistent development environments by integrating a vast number of packages and libraries into user projects. However, the persistent disk attached to all development containers has grown significantly, reaching 20TB, necessitating a solution to manage this growth without sacrificing backward compatibility. To address this, Replit implemented Tvix, a modular version of Nix, which includes the Tvix store backed by the tvix-castore. This system uses content addressing and chunking to store only unique data chunks, significantly reducing storage requirements. By mounting a compressed Tvix store on a FUSE filesystem, Replit managed to compress its 6TB cache into 1.2TB, reducing storage costs by 90%. The Tvix project, supported by Replit and the Tvix community, is open-source, and Replit encourages individuals interested in solving similar challenges to join their team.