Tutorials System Design Tutorial
Repository Pattern in Enterprise Apps — Complete Guide
Repository Pattern in Enterprise Apps — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of System Design Tutorial on Toolliyo Academy.
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System Design Tutorial · Lesson 75 of 100
Repository Pattern in Enterprise Apps
Basics ✓ → Scale ✓ → Interview
Interview · 3 — Case studies · ~10 min · Module 8: Low-Level Design
What is this?
A repository hides data access behind a collection-like interface so application code does not speak SQL/ORM everywhere.
Why should you care?
ShopNest use-cases stay testable and storage can evolve without rewriting every handler.
See it live — copy this example
Sketch the architecture on paper. These lessons focus on concepts and trade-offs.
IOrderRepository:
Get(id), Add(order), Save()
Impl: EfOrderRepository / SqlOrderRepository
Handler depends on interface onlyRun Example »
This lesson uses terminal or setup steps. Run commands on your computer — the live editor appears on coding lessons.
What happened?
- Repositories express domain retrieval needs, not every table join.
- Do not make a repository per table automatically if aggregates differ.
Practice next
- Define IOrderRepository for ShopNest.
- build with your ORM/SQL.
- Fake it in unit tests.
- Add FindOpenByUser method.
- Swap impl in integration tests.
Remember
Hide storage behind ports. Test with fakes. Model aggregates, not only tables.
Order repository port
ShopNest handlers call IOrderRepository.
Outcome: SQL changes stay in one place.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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