Same here. We migrated from 5 repositories down to a single one in 2013, and have been working with a simple PR process (first Phabricator, then Bitbucket) ever

Same here. We migrated from 5 repositories down to a single one in 2013, and have been working with a simple PR process (first Phabricator, then Bitbucket) ever since, along with a TeamCity as a CI to run tests and deploy. We do try to minimize our "technological footprint" by reducing the number of languages, tools, third party packages, etc. But I would say our main strategy is to enforce static analysis everywhere. Global type-checking between C# and F# projects comes out-of-the-box (but you have to design the shared types properly), and we produce TypeScript contracts and signatures out of C# contracts and API endpoints.