I work on a product in payments, specifically a client-side checkout application. It's essentially responsible for collecting data from the user (billing and sh

I work on a product in payments, specifically a client-side checkout application. It's essentially responsible for collecting data from the user (billing and shipping addresses, affordability information, etc.), presenting the various payment methods and displaying up sell stuff after completing the purchase. Just the client side application is about 250000 lines of code, not including third party stuff. It feels like applications grow with the team that develops it. At our peak, we were around 10 people working on it, and it's just so hard to do meaningful refactoring when large parts of the codebase are being modified by 10 people in parallel. Not only the technical challenge, but also getting everyone to agree on and embrace patterns and structure.