What distinguishes a monolithic application from a microservices architecture?

The distinction between a monolithic application and a microservices architecture primarily revolves around their structural characteristics. A monolithic application is designed as a single, unified unit, where all components are interwoven and operate as one entity. This means that the user interface, business logic, and data access layer are all packaged together, making deployment simpler, but at the cost of scalability and flexibility.

In contrast, microservices architecture breaks down applications into smaller, independent services that communicate over well-defined APIs. Each microservice focuses on a specific business functionality, which allows for more granular scaling, easier updates, and improved fault isolation among different parts of the application. This modularity is what enables teams to develop, deploy, and scale services independently.

The other options presented relate to misconceptions about maintenance ease, service size, and agility, but they don’t accurately capture the core defining feature of monolithic applications compared to microservices. Understanding these architectural principles is crucial for effectively leveraging each model's strengths according to project requirements.