How to distinguish a monolithic application from a system built on microservices, and what are their main differences?

A monolithic application is a single unit where all components and functionalities are combined in one process or codebase. Microservice architecture is a set of independent services, each responsible for a specific business function and interacting with others via APIs.

Main differences:

• Code separation:

  • Monolith — one large codebase.
  • Microservices — many small services.

• Deployment:

  • Monolith is deployed as a whole.
  • Microservices can be deployed and updated independently.

• Scaling:

  • Monolith scales as a whole.
  • Microservices scale individually, which is more efficient.

• Testing:

  • In monoliths, tests cover the entire system.
  • In microservices, each service is tested separately and integratively.

• Complexity:

  • Monoliths are simpler initially but harder to maintain as they grow.
  • Microservices are more complex to organize but offer flexibility and resilience.

Example: if a failure occurs in one module of a monolith, it can affect the entire system. In microservices, a failure in one service does not necessarily impact others.

Thus, a monolith is a single application, while microservices are a distributed system of independent components.