Securing an API platform involves prioritizing the security, governance, and reliability of the architecture by using tools like Kong Gateway and Kong Mesh. Kong Gateway serves as a secure entry point for north-south traffic, managing the lifecycle of APIs and ensuring they are protected from direct access. The deployment of a sandbox environment using Kubernetes, with minikube and the Kong Ingress Controller, is demonstrated to facilitate this setup. The guide also emphasizes the significance of microservices design to avoid monolithic structures, promoting reusability and scalability through minimal APIs. As the complexity of managing inter-service communication grows, implementing a service mesh such as Kong Mesh becomes crucial for securing east-west traffic. By enabling zero trust and using mTLS, the platform ensures that all internal communications are controlled and unauthorized access is prevented. The step-by-step process includes creating traffic permissions to govern communication between services like demo-app and Redis, highlighting the importance of both north-south and east-west traffic security in API management.