Building scalable APIs in cloud-native environments involves adopting principles that ensure resilience, flexibility, and long-term reliability. As API usage grows, challenges such as increased request volumes and latency can arise, making cloud-native design essential. This approach emphasizes modularity, automation, observability, and stateless services to handle fluctuating demands and ensure smooth operation. Key infrastructure strategies include containerization, orchestration with Kubernetes, auto-scaling, and using infrastructure as code for consistency. Tools like Blackbird can aid in testing and simulating complex dependencies, allowing developers to build APIs that can grow from day one without the pitfalls of traditional systems, such as tightly coupled services and inadequate failure planning. By integrating these principles and tools, developers can craft APIs that are robust, scalable, and responsive to user demands.