Building a serverless function or an API is easy. However, things get a bit more complicated as your application grows. What works for a few functions often don't work for hundreds of functions. As your application grows, you'll need to evolve your architecture, deployment, monitoring, and many other things. This talk is a case study of an evolution of the serverless startup's architecture. We started with a single Lambda function in early 2018 and evolved our application through multiple stages and architectures. At the moment application uses GraphQL and more than 100 Lambda functions and serves millions of requests. We faced and solved many issues during the last three years, learned many things, and managed to keep our infrastructure costs low.