Module
Module 4 of 6Lesson 1 of 2~16 min

Frontend, backend and API, who does what

Lesson 1 of the module "From frontend to database" in the course "Explain how a web product works, from browser to server".

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Lesson objective

By the end of this lesson, you will be able to split a feature's responsibilities between frontend, API and backend, read a JSON data exchange and justify that a business or security rule is checked on the server side.

Where it fits

From frontend to database

Who does what in a web product, and where must each rule run?

Lessons in this module

  1. Frontend, backend and API, who does what (this lesson)
  2. Behind the API, data, files and third-party services

What you will learn in the course

This lesson is part of the course Explain how a web product works, from browser to server

  • Describe the steps of a web request, from the typed address to the displayed page (URL, DNS resolution, encrypted connection, HTTP request and response, browser rendering).
  • Read an HTTP exchange in the browser's Network tab (method, URL, status code, headers, cookies, duration) and draw a first diagnosis from it.
  • Explain how responsibilities are split between browser, frontend, backend, API, database and third-party services, and place where a business rule must run.
  • Explain the role of a CDN and of caches (browser, CDN, server) and anticipate their effects on speed, data freshness and releases.
  • Tell apart local, preview, staging and production environments, and say what changes from one to another (configuration, data, secrets).
  • Place a symptom (slowness, blank page, error, stale data) in the right layer and ask the technical team precise questions.
  • Produce the annotated diagram of a request's journey through your own product and have it validated by a developer.

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