Tutorials Software Architect Tutorial
HLD vs LLD
HLD vs LLD: free step-by-step lesson with examples, common mistakes, and interview tips — part of Software Architect Tutorial on Toolliyo Academy.
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Software Architect Tutorial · Lesson 3 of 100
HLD vs LLD
Foundations & Styles → Distributed & Data → Cloud & Quality → Leadership & Cases
Foundations & Styles · 1 — Decide · ~6 min · Architecture Foundations
What is this?
HLD (high-level design) shows major components, data stores, and flows. LLD (low-level design) covers classes, APIs, schemas, and sequences inside a component.
Why should you care?
Mixing them confuses stakeholders. Architects lead HLD; LLD is often owned with senior engineers per service.
See it live — copy this example
These are architecture exercises: fill templates, draw boxes, write ADRs. No cloud bill required.
# HLD box
[Client] -> [API Gateway] -> [Order Service] -> [Orders DB]
\-> [Payment Service]
# LLD (Order Service only)
OrderController -> OrderAppService -> OrderRepository -> Orders DBWhat happened?
- HLD stops at services and stores.
- LLD zooms into one service’s internal structure.
Practice next
- Draw HLD for your platform “create order”.
- Pick one service and sketch LLD classes.
- List what belongs only in HLD.
- Add a failure arrow on HLD.
- Add an interface on LLD.
Remember
HLD = system map. LLD = inside one boundary. Keep audiences separate.
Interview split
HLD round then LLD round.
Outcome: You do not dump class details into the system diagram.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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