In version-control systems, a monorepo ("mono" meaning 'single' and "repo" being short for 'repository') is a software-development strategy in which the code for a number of projects is stored in the same repository.
[2] Google,[3] Meta,[4] Microsoft,[5] Uber,[6] Airbnb, and Twitter[7] all employ very large monorepos with varying strategies to scale build systems and version control software with a large volume of code and daily changes.
[4] Google's monorepo, speculated to be the largest in the world, meets the classification of an ultra-large-scale system[3] and must handle tens of thousands of contributions every day in a repository over 80 terabytes in size.
[19] Due to scaling issues, Google eventually developed its own in-house distributed version control system dubbed Piper.
[23] Twitter began development of Pants in 2011, as both Facebook's Buck and Google's Bazel were closed-source at the time.