Which of the following cloud-native architecture designs is the most easily maintained, decentralized, and decoupled?

Microservices is an architectural style that structures an application as a collection of small, autonomous, and loosely coupled services. Each service is self-contained, runs its own process, and communicates with others through well-defined APIs. This inherent modularity allows individual services to be developed, deployed, and maintained independently without impacting the entire system. This design directly promotes decentralization (no single point of control), decoupling (minimal dependencies), and easier maintenance, as changes are isolated to specific services. This contrasts sharply with monolithic architectures, which are centralized and tightly coupled.

A. Monolithic: This architecture is a single, tightly coupled unit, making it difficult to maintain and inherently centralized, the opposite of the requirements.
B. Hybrid cloud: This describes a cloud deployment model (a mix of public and private infrastructure), not an application architecture design.
C. Mainframe: This refers to a type of centralized computing hardware and its associated legacy software models, not a modern, decentralized cloud-native architecture.

1. National Institute of Standards and Technology (NIST). (2018). NIST Special Publication 500-322: Foundational Elements of the Microservices Architecture. Section 2.1, "Characteristics of Microservices," states: "Microservices are loosely coupled... Each microservice can be deployed, upgraded, scaled, and restarted independently of other services in the application." This directly supports the principles of being easily maintained and decoupled.

2. Microsoft Azure Architecture Center. (2024). Microservices architecture style. In the "Benefits" section, it lists "Independent deployments," "Independent development," and "Decentralized governance" as key advantages, which align with the concepts of being easily maintained, decoupled, and decentralized.

3. Amazon Web Services (AWS). (n.d.). What are Microservices?. The documentation states, "Microservices are an architectural and organizational approach to software development where software is composed of small independent services that communicate over well-defined APIs." It highlights benefits like "Improved scalability" and "Increased agility," which are direct results of the decoupled and decentralized nature of the architecture.