We don't always have the opportunity to create applications from scratch. Most systems are legacy and there is nothing wrong about it. These are proven solutions that bring profits to companies every day. Problems start when they need to be extended with new functionalities that we want to implement in modern, cloud-native technologies. In this talk, I will present how to integrate serverless solutions with existing systems. I will tell you what problems we encountered during the implementation and how they can be solved. In summary, I will discuss how the serverless way of building software was perceived by project stakeholders and what value it delivered to the organization.