Why should database design be completed before application development?

Why should database design be completed before application development?

An initial database design helps developers agree on what information the application stores and how that information relates. Completing a useful baseline before feature implementation reduces the chance that each screen invents a different version of the same data.

Start from product behavior

For a wedding-management application, list the actions users need to perform: create a wedding, schedule events, assign tasks, invite guests, and record responses. Then identify the records and relationships those actions require.

This exercise exposes important questions early. Can one user help manage multiple weddings? Can a guest attend one event but decline another? Does a task belong to the whole wedding or a specific event? These answers affect more than field names.

Define ownership and valid states

Record which entity owns each piece of information, which fields are required, and what values are allowed. A task might have a wedding identifier, an optional event identifier, an assignee, a due date, and a status.

Specify that linked events and assignees must be valid for the same wedding. Also define what happens when a referenced record is archived or removed. Without those decisions, developers may create orphaned records or contradictory behavior.

Treat the design as a reviewed starting point

“Completed” should mean sufficiently clear for the next implementation increment, not permanently frozen. A prototype may reveal that a relationship needs revision or a query needs another index.

Ask AI to walk through sample user journeys against the proposed model and identify missing information. Review its suggestions with realistic examples before coding. When the design changes, update both documentation and migration plans so application code and stored data remain consistent.