System Design

What is System?

• Architecture or Collection of technologies serves a certain set of users to fullfill a certain set of requirements
• Collection of Components that serves a certain set of users to fulfill a certain set of requirements

graph LR;
subgraph A[System]
end
F(Architecture or <br/>Collection of technologies)--serves-->B[set of users]--to fulfill-->C[set of requirements]

Computing Systems

graph LR;
X[System]
Servers-->X
Databases-->X
Caches -->X
Applications-->X
A[Message Queues]-->X
X-->NF
X-->WA
X-->FB
X-->TW

What is Design

• understanding the user requirements and selecting the components ,modules and software technologies,how they are going to be interact with each other to fullfill the requirements

System Design

• Understanding the user requirements and selecting the components ,modules and software technologies,how they are going to be interact with each other to fullfill the requirements

Why System Design

• To handle the scale
• To handle the complexity
• To handle the reliability
• To handle the availability
• To handle the performance
• To handle the security
• To handle the maintainability
• To handle the cost
• To handle the time to market
• To handle the user experience
• To handle the user requirements

How to do System Design

• Understand the user requirements
• Understand the scale
• Understand the complexity
• Understand the reliability
• Understand the availability
• Understand the performance
• Understand the security
• Understand the maintainability
• Understand the cost

Components of System Design

• Components
• Modules
• Software Technologies
• Hardware Technologies
• Network Technologies
• Storage Technologies

What is System Design

• Process of designing the element of a system (app,website,web app) such as Architectures,Modules and Components ,the different Interfaces of those components and the Data that goes through the system.

Types

graph TD;
A[System Design]-->B[HLD <br>High Level Design]
A-->C[LLD<br>Low Level Design]
subgraph HLD
X[Describes the main components that would be<br>developed for the resulting project <br> <br> The system architecture details,database design<br>services and processes the relationship between<br>various modules and features.]
end
subgraph LLD
Y[Describes the design of each elements mentioned<br>in the HLD of the system.Classes,Interfaces,<br>relationship between different classes and actual<br>logic of the various components]
end

Architecture

• Internal Design Details for buliding the applications

graph
A[Types of Architecture]-->B[Monolithic]
A-->C[MicroServices]

graph TD;
subgraph Monolithic
a[Frontend]-->A
b[Backend]-->A
c[Database]-->A
A[System]
end
subgraph Microservices
a1[Frontend]-->X[System 1]
b1[Backend]-->Y[System 2]
c1[Database]-->Z[System 3]
end

Monolithic Architecture

• Single Unit
• Single Code Base
• Single Deployment
• Single Database
• Single Unit Testing
• Single Unit of Scaling
• Single Unit of Failure
• Single Unit of Maintainance

Advantages of Monolithic Architecture

• Single Unit of Deployment
• Single Unit of Scaling
• Integration testing is easy
• Esier to secure
• Fewer Network Calls
• Easy to deploy
• Less Confusion

Disadvantages of Monolithic Architecture

• Single Unit of Failure can bring down the entire system
• Single module update requires the entire system to be deployed
• Any change in single module's programming language requires the entire system to be deployed
• Single Database so more chances of data corruption or more calls to database

Distributed System/Microservices Architecture

• collection of multiple individual services that communicate with each other over the network to achieve a common goal

graph TD;
subgraph Microservices
a1[Frontend]-->X[System 1]
b1[Backend]-->Y[System 2]
c1[Database]-->Z[System 3]
a2[Frontend]-->W[System 4]
b2[Backend]-->V[System 5]
c2[Database]-->U[System 6]
a3[Frontend]-->T[System 7]
b3[Backend]-->S[System 8]
c3[Database]-->R[System 9]
X-->Y
Y-->Z
Z-->W
W-->V
V-->U
U-->T
T-->S
S-->R
R-->X
end

• If any of the system fails then the entire system will not fail
• It will jump to next system/replica

graph TD;
subgraph Microservices
a1[Replica]-->X[System 1]
b1[Replica]-->Y[System 2]
c1[Replica]-->Z[System 3]
a2[Replica]-->W[System 4]
b2[Replica]-->V[System 5]
c2[Replica]-->U[System 6]
a3[Replica]-->T[System 7]
b3[Replica]-->S[System 8]
c3[Replica]-->R[System 9]
X-->Y
Y-->Z
Z-->W
W-->V
V-->U
c2-->T
T-->S
S-->R
R-->X
end

Advantages of Microservices Architecture

• Easy to scale
• No single point of failure

Disadvantages of Microservices Architecture

• Complex
• Management of multiple services requires more resources
• Integration testing is difficult
• Difficult to secure
• More Network Calls
• Message may be lost in b/w nodes/services