Components of System Design | System Design Tutorials | Part 2 | 2020

Part 2 of Yogita Sharma System Design Tutorial.

Components are the basic building blocks of system and consist of two types:

1. Logical Entities
2. Tangible Entities

Logical Entities:

• At the core of logical entities is data, which is stored in databases. 
• Users can interact with databases via applications,
• Typical operations are create, read, update, delete (CRUD)
• Applications and databases use communication protocols, which are also logical entities
• Communication protocols such as HTTP, TCP/IP over networks
• The presentation (front-end) application communicates to the server (on a separate machine) via protocols such as HTTP, RPC, APIs
• Some systems, such as logging systems, do not have presentation layer
• All of these logical entities run on computers, often on a machine run by a cloud provider
• Examples of logical entities include:
• Data
• Database
• Application
• Cache
• Message Queues
• Infra
• Communication

Tangible Entities:

• Examples of logical tangible include
• Text, images, videos
• MongoDB, MySQL, Cassandra
• Java, Golang, Python, React
• Redis, MemCache
• Kafka, RabbitMQ
• AWS, Google Cloud Platform, Azure
• APIs, RPCs, Messages
• Cloud providers instantiate tangible entities listed above in order to provide a working environment for businesses to provide services to other businesses or users 
• A simple system setup is shown below:

Courtesy of  vasanthk Gist

• The Request could come from the user via front-end app on mobile, laptop, etc via browser or dedicated application.
• Physical computers provisioned by cloud providers run the load balancers, web servers, and databases that data and respond to the user.
• The physical and tangible entities in the diagram above as often referred to as "infrastructure".