Why Google Stores Billions of Lines of Code in a Single Repository

Google's monolithic repository provides a common source of truth for tens of thousands of developers around the world.

This article outlines the scale of Google’s codebase, describes Google’s custom-built monolithic source repository, and discusses the reasons behind choosing this model. We provide background on the systems and workflows that make managing and working productively with a large repository feasible. We also review the advantages and trade-offs of this model of source code management.