What is Repository Pattern?

What is the Repository Pattern?

The Repository pattern collects data access operations in a separate layer. Instead of writing SQL, ORM calls, or external API handling directly inside business logic, the application talks to interfaces such as UserRepository or OrderRepository.

This hides where the data actually lives. A record read from PostgreSQL today may later come from another service or a cache layer; higher application layers should not need to know about that change.

How Does it Work?

A repository usually sits between the service or domain layer and the data source:

1. The service layer calls an intent-based method such as “find customer” or “save order”.
2. The repository builds the query or API request.
3. Raw data is mapped into the model used by the application.
4. Errors, transactions, and connection details stay in one place.

In applications using MVC, a controller can stay thinner when it calls a repository instead of building database queries itself.

When is it Useful?

The Repository pattern is useful when data access rules become complex, tests need fake data sources, or the same data is read from multiple places. Finance, inventory, order, and customer account modules often benefit because the code expresses business intent more clearly.

Adding a repository for every tiny CRUD screen can also create unnecessary abstraction. This design pattern is valuable when it reduces real data access complexity, not when it only renames simple database calls.