LPI Web Dev Essentials: Software Development and Web Technologies

This domain is the conceptual foundation of the LPI Web Development Essentials exam. It tests whether you understand how browser, server, and network cooperate, how projects are versioned and organized, and how patterns such as MVC and REST shape the code you write.

How a page is delivered

• A URL carries a scheme, host, optional port, path, and query string.
• HTTP is a stateless request/response protocol. Methods carry intent: GET reads, POST creates, PUT replaces, PATCH partially updates, DELETE removes.
• Status codes are grouped: 2xx success, 3xx redirection, 4xx client error, 5xx server error. 401 means not authenticated; 403 means authenticated but forbidden.
• HTTPS wraps HTTP in TLS so content is protected in transit; it does not make the application itself secure.

Architecture and workflow

• Front-end code runs in the browser; back-end code runs on the server and talks to databases.
• MVC separates the model (data), the view (presentation), and the controller (request handling).
• REST APIs expose resources over HTTP and usually exchange JSON.
• Git records snapshots: add stages, commit records, branch isolates work, merge integrates it.

Worked example

A browser opens https://shop.example.com/api/items?page=2. Reasoning: DNS resolves the host to an IP, TCP connects on port 443, TLS negotiates, then the browser sends GET /api/items?page=2 because it is retrieving data, not changing it. The controller queries the model and returns 200 with a JSON array that the front-end renders. Had the caller lacked credentials, the correct code would be 401, not 404.

Traps

Marks are lost for treating GET as a way to modify data, mixing up 401 and 403, calling POST idempotent (PUT and DELETE are), and assuming CORS is server-side access control - browsers enforce it. Remember that HTTP is stateless: sessions depend on cookies or tokens, not on the server recalling earlier requests.