Tutorials System Design Tutorial
Enterprise LLD Patterns — Complete Guide
Enterprise LLD Patterns — 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 80 of 100
Enterprise LLD Patterns
Basics ✓ → Scale ✓ → Interview
Interview · 3 — Case studies · ~10 min · Module 8: Low-Level Design
What is this?
Enterprise LLD patterns combine repositories, UoW, messaging ports, policies, and mapping at edges into a consistent service style.
Why should you care?
ShopNest services look familiar to every engineer when LLD patterns are shared.
See it live — copy this example
Sketch the architecture on paper. These lessons focus on concepts and trade-offs.
Handler → Policy → Domain
↘ IRepository / IEventPublisher
DTO mappers at API edge
Cross-cutting: authz, validation, logging behaviorsRun Example »
This lesson uses terminal or setup steps. Run commands on your computer — the live editor appears on coding lessons.
What happened?
- A standard vertical slice reduces debate.
- Policies encode rules; publishers abstract the bus.
- Keep it pragmatic, not ceremonial.
Practice next
- Document the ShopNest service LLD template.
- Include repo + outbox publisher ports.
- Validate and authz as pipeline behaviors.
- Generate a new service from the template.
- Add a checklist to code review.
Remember
Shared LLD template. Ports for IO. Pragmatic layers.
Orders service template
ShopNest clones the LLD skeleton for Returns.
Outcome: Returns ships with familiar structure and ops hooks.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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