TestFlight
Apple's service for distributing test builds of iOS apps outside the App Store — up to 10,000 external testers.
The service existed as a standalone product before Apple bought it in 2014 and folded it into App Store Connect. Internal testers on the development team get builds immediately, while external testers are invited by link and require a lighter review of the first build.
Each build number is valid for 90 days, which forces regular updates during a test period. TestFlight is in practice also the only way to let anyone outside the company try an iOS app without publishing it — a clear example of how the walled garden shapes the workflow, since the Android equivalent is simply sending an APK file.