In the software development lifecycle of a web application, the connectivity between the frontend and backend is established during the Integration phase.
This phase is responsible for connecting the user interface (frontend) with the server-side logic (backend) so that data can be exchanged seamlessly.
APIs, RESTful services, and database connections are implemented in this phase to enable proper communication between the client and the server.
The integration ensures that user actions on the front end are reflected correctly in the backend operations and database transactions.
Without this phase, the application would remain incomplete and non-functional.