A cloud engineer is designing a cloud-native, three-tier application. The engineer must adhere to the following security best practices:• Minimal…

Microservices architecture is a design approach where a single application is composed of many loosely coupled and independently deployable smaller services. This design directly meets the requirement for "minimal services," as each microservice is built to perform a single function, thus reducing the attack surface. This architectural style promotes vendor agnosticism because the services are self-contained and can be packaged in containers (e.g., Docker), making them portable across different cloud environments. The use of virtualization is a common underlying infrastructure layer for hosting these containerized microservices.

A. Virtual machine: A virtual machine is a foundational infrastructure component, not an architectural design concept. It can host numerous services, which contradicts the "minimal services" principle.
C. Fan-out: This is a specific messaging pattern used in event-driven architectures to deliver a message to multiple destinations; it is not a comprehensive system design concept that meets all requirements.
D. Cloud-provided managed services: Using these services directly opposes the "vendor agnostic" requirement, as it creates a dependency on a specific cloud provider's proprietary offerings and APIs.

1. National Institute of Standards and Technology (NIST). (2020). Special Publication (SP) 800-204A, Building Secure Microservices-based Applications Using Service-Mesh Architecture. Section 2.1, "Microservices Characteristics," states that services are "Small in size and focused on a single capability," which aligns with the minimal services principle. The inherent decoupling facilitates portability.

2. Patterson, D., & Joseph, A. (2020). CS 162: Operating Systems and System Programming, Lecture 21: Distributed Systems. University of California, Berkeley. Slide 60 discusses microservices as independently deployable components, a key attribute for achieving portability and vendor-agnostic solutions.

3. Lewis, J., & Fowler, M. (2014). Microservices. martinfowler.com. This foundational document on software architecture, widely cited in academic contexts, explains that microservices are "organized around business capabilities" and are "independently deployable," which supports the principles of minimal services and portability required by the question.