Module
Module 4 of 6Lesson 2 of 2~12 min

Behind the API, data, files and third-party services

Lesson 2 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 describe what sits behind an API (database, file storage, third-party services, background jobs, logs) and choose, for a feature, what must happen during the request and what can happen in the background.

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
  2. Behind the API, data, files and third-party services (this lesson)

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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