Modularity

is the name given, to the process of defining the components, parts, or modules into which a system or software can be divided.

• Ex: Breaking large monolithic applications into separate and smaller parts
  Advantages:
• Scalability: It is better to have two applications at 40% than one at 80%.
• Agility: It is easier to respond to changes in the system (attention to coupling).
• Speed-to-market: Domain modules facilitate business changes in the system.
• Availability (Fault Tolerance): If one module fails, the others can continue to work.
• Deployability: More frequent deployments with less risk to the system (attention on coupling)
• Testability: It is easier and faster to test small modules thoroughly.
• Maintainability: Easy to add, change, and remove features. (ex: patches)
  Attention points:
• The scalability and elasticity can suffer with increased communication between the services.
• With an increase in the number of modules, it is better to consider asynchronous communication.
• Asynchronous communication favors fault tolerance, scalability, and elasticity.