Cianplan

Level 0: Orientation & prerequisites · L0.0 Welcome: what system design is and how to learn it here

Software from the inside: client, server, database and API

Name the four pieces behind any app (client, server, database and API) and explain what each one does, using a food delivery order.

12 min · Free

What you take away

  • The client is the app or website on your device: it shows information and sends requests, but keeps little of the real data.
  • The server is a computer somewhere else that receives requests, applies the business rules and decides the answer.
  • The database keeps information safe and easy to find, so it survives restarts and is shared by every user.
  • The API is the contract between client and server: the list of requests the server accepts and what each one returns.
  • The cloud is renting someone else's computers; code is the instructions, and infrastructure is the machines and network the code runs on.

How the class is laid out

  1. The problem
  2. The simple version
  3. One order, piece by piece
  4. What “the cloud” means
  5. Code versus infrastructure
  6. The whole picture
  7. Check your understanding