Difference between High Level Design(HLD) and Low Level Design(LLD) (original) (raw)

Last Updated : 16 Apr, 2026

System design involves creating both a High-Level Design (HLD), which is like a roadmap showing the overall plan, and a Low-Level Design (LLD), which is a detailed guide for programmers on how to build each part.

It ensures a well-organized and smoothly functioning project.
High-Level Design and Low-Level Design are the two main aspects of System Design.

High Level Design(HLD)

High-level design or HLD describes the overall architecture of a system and shows how different components interact. It outlines major modules, system structure, and relationships between services.

HLD includes:

System architecture showing the major components and their interactions.
Database design and high-level data flow between modules.
Overview of systems, services, platforms, and their relationships.
Description of hardware, software interfaces, and user interfaces.
User workflow and key performance considerations.

Low Level Design(LLD)

LLD or Low-Level Design, is a phase in the software development process where detailed system components and their interactions are specified.

It describes detailed description of each and every module means it includes actual logic for every system component and it goes deep into each modules specification.
It is also known as micro level/detailed design.
It is created by designers and developers.
It involves converting the high-level design into a more detailed blueprint, addressing specific algorithms, data structures, and interfaces.
LLD serves as a guide for developers during coding, ensuring the accurate and efficient implementation of the system’s functionality.

High Level Design Vs Low Level Design

High Level Design (HLD) defines the overall system architecture, while Low Level Design (LLD) explains the detailed internal logic and component-level implementation.

HIGH-LEVEL DESIGN	LOW-LEVEL DESIGN
High Level Design is the general system design means it refers to the overall system design.	Low Level Design is like detailing HLD means it refers to component-level design process.
High Level Design in short called as HLD.	Low Level Design in short called as LLD.
It is also known as macro level/system design.	It is also known as micro level/detailed design.
Furthermore, it describes the overall description/architecture of the application.	It describes detailed description of each and every module.
High Level Design expresses the brief functionality of each module.	Low Level Design expresses details of functional logic of the module.
It is created by solution architect.	It is created by designers and developers.
Here in High Level Design the participants are design team, review team, and client team.	Here in Low Level Design participants are design team, Operation Teams, and Implementers.
It is created first means before Low Level Design.	It is created second means after High Level Design.
In HLD the input criteria is Software Requirement Specification (SRS).	In LLD the input criteria is reviewed High Level Design (HLD).
In HLD the output criteria is database design, functional design and review record.	In LLD the output criteria is program specification and unit test plan.