Why is Primary keys important in Laravel applications, and what problem does it solve for developers?

Why is Primary keys important in Laravel applications, and what problem does it solve for developers? The key reason to understand primary keys is that Laravel applications are usually composed of several layers that must work together predictably. Models normally expect a primary key and can be configured when a schema uses a different key structure. Ignoring that boundary can lead to duplicated logic, poor security, unnecessary database work, or code that is difficult to test. Why it matters in practice: Eloquent models represent application data and provide expressive methods for querying, persisting, relating and transforming database records. The specific focus here is primary keys: Models normally expect a primary key and can be configured when a schema uses a different key structure. This question is designed to test not only terminology, but also how the concept fits into Laravel's request, application, database, security, or deployment workflow.