Full Stack Web Development Flashcards

Question 1

What is the basic model that web applications use to exchange information?

Accepted Answer

The web mostly follows the client-server model. A client, usually a browser, sends a request over the network to a server, which processes it and returns a response, often containing HTML, JSON, or other data. This request-response cycle repeats for every page load, form submission, or background update.

Question 2

What do HTTP methods such as GET and POST tell a server about a request?

Accepted Answer

HTTP methods describe the intended action of a request. GET asks the server to retrieve a resource without changing it, while POST sends data to be processed, such as a submitted form or new record. Choosing the correct method keeps applications predictable.

Question 3

What is the role of HTML, CSS, and JavaScript in a web page?

Accepted Answer

HTML provides the structure and meaning of content, such as headings, paragraphs, and links. CSS controls presentation, including layout, colors, and spacing. JavaScript adds behavior, responding to user actions and updating the page without a full reload. Together, these three technologies form the basis of every front-end interface.

Question 4

What does it mean for a URL to identify a resource on the web?

Accepted Answer

A Uniform Resource Locator, or URL, is an address that names a specific resource, such as a page, image, or API endpoint. It typically includes a scheme like https, a host name that identifies the server, an optional port, and a path that points to the resource.

Question 5

Why do browsers and servers use status codes in responses?

Accepted Answer

Status codes are three-digit numbers that summarize the outcome of a request. Codes in the 200 range indicate success, 300 range redirection, 400 range client errors such as a missing page, and 500 range server errors. Developers rely on these codes to decide what to display and when to retry.

Question 6

What is a cookie, and why does a server set one?

Accepted Answer

A cookie is a small piece of data that a server sends to the browser, which stores it and returns it with later requests to the same site. Servers use cookies to maintain state across requests, which HTTP does not do by itself. Because cookies travel with every request, configure them carefully.

Question 7

Why is HTTP described as a stateless protocol?

Accepted Answer

HTTP is stateless because each request is handled independently, and the server does not automatically remember anything about earlier requests from the same client. This keeps servers simple and easy to scale, since any server instance can handle any request. Developers add memory of users through mechanisms like cookies, tokens, or server-side sessions.

Question 8

How does a single web page request travel from browser to server?

Accepted Answer

The browser first resolves the domain name through DNS to find an IP address, then opens a connection, usually over TLS, and sends an HTTP request. The server routes the request to application code, which may query a database, and returns a response. The browser parses that response, requests linked assets, and renders the page.

Question 9

What is the difference between a static page and a dynamic page?

Accepted Answer

A static page is delivered exactly as stored on the server, so every visitor sees the same content. A dynamic page is generated or modified for each request, often using data from a database or the user's session. Many applications combine both approaches, serving prebuilt shells while loading personalized content in the browser.

Question 10

What is the Document Object Model, and how does JavaScript use it?

Accepted Answer

The Document Object Model is a tree-shaped representation of an HTML document in which each element, attribute, and text fragment is a node. JavaScript reads and changes this tree to update content, styles, and structure without reloading the page. Events such as clicks let code respond to users.

Question 11

Why do component-based frameworks like React split interfaces into components?

Accepted Answer

Component-based frameworks divide an interface into reusable pieces, each responsible for one part of the screen, such as a button, card, or navigation bar. Components make code easier to test, reason about, and reuse across pages. When data changes, the framework updates only the affected components, which keeps the interface responsive.

Question 12

What does responsive design mean in front-end development?

Accepted Answer

Responsive design is an approach in which a page adapts its layout to the size and capabilities of the device viewing it. Developers use flexible grids, relative units, and CSS media queries to rearrange content for narrow and wide screens. The viewport meta tag is needed so mobile browsers scale the page correctly.

Question 13

What is the purpose of client-side form validation, and what is its limit?

Accepted Answer

Client-side validation checks form input in the browser before submission, giving users immediate feedback about missing or malformed fields. It improves the experience, but it cannot be trusted alone because any user can bypass browser code or send requests directly. The server must validate the data again before storing or acting on it.

Question 14

How does accessibility affect the markup a developer writes?

Accepted Answer

Accessibility depends on semantic markup, meaning that elements such as buttons, headings, and lists are used for their intended roles. Assistive technologies like screen readers rely on these roles to convey structure and interactive controls. Adding alt text to images and labels to form fields helps people who cannot see the visual layout.

Question 15

What is application state in a front-end user interface?

Accepted Answer

Application state is the data that describes what the interface currently shows, such as the items in a cart, the open menu, or the text typed into a field. When state changes, the interface is updated to reflect it. Keeping state predictable, and in one clear place where possible, makes applications easier to debug.

Question 16

How does a single-page application differ from a multi-page application?

Accepted Answer

A multi-page application loads a new HTML document from the server for each major navigation. A single-page application loads one shell and then updates the view with JavaScript, often fetching data through an API. This feels faster after the first load but adds work for search indexing, routing, and managing browser history.

Question 17

What is the main job of a backend server in a web application?

Accepted Answer

A backend server receives requests, enforces business rules, performs authentication, and coordinates access to data. It keeps sensitive logic and credentials away from the browser, where users can inspect or change them. The backend also returns responses in a format the frontend can use, commonly JSON.

Question 18

What is a REST API, and what does it mean for a resource to be addressable?

Accepted Answer

A REST API exposes resources, such as users or orders, through URLs and standard HTTP methods. Each resource is addressable, meaning it has its own URL that clients can use to read or change it. REST is an architectural style rather than a strict protocol, so teams often adapt its conventions.

Question 19

Why should passwords be hashed rather than stored as plain text?

Accepted Answer

Passwords should be hashed so that a leaked database does not reveal usable credentials. Hashing transforms a password with a one-way function, so the original cannot be read back from the stored value. Servers should use a slow, purpose-built password hashing algorithm with a unique salt for each user.

Question 20

What is the purpose of middleware in a server framework?

Accepted Answer

Middleware is code that runs between receiving a request and producing a response, handling shared tasks such as logging, parsing request bodies, checking authentication, or setting headers. Each middleware function can inspect or modify the request, pass it onward, or end the cycle early with an error.

Question 21

What does it mean for an API endpoint to be idempotent?

Accepted Answer

An idempotent operation produces the same result no matter how many times it is repeated with the same input. GET and PUT are designed this way, so a client can safely retry them after a network failure. POST is generally not idempotent, since repeating it might create duplicate orders or charges.

Question 22

What is CORS, and why do browsers enforce it?

Accepted Answer

Cross-Origin Resource Sharing is a browser mechanism that controls whether a page from one origin may read responses from a different origin. Browsers enforce it to protect users from malicious sites reading private data from other sites they are signed into. Servers opt in by sending specific headers that name the allowed origins.

Question 23

What is the purpose of environment variables in a backend project?

Accepted Answer

Environment variables store configuration values, such as database addresses, API keys, and feature settings, outside the source code. This lets the same codebase run in development, testing, and production with different settings. Secrets kept in environment variables should never be committed to version control, because anyone with repository access could read them.

Question 24

How should a backend handle errors so that clients get useful responses?

Accepted Answer

The backend should return an appropriate status code and a consistent error body that describes the problem without exposing internal details. Stack traces, database messages, and file paths are useful to developers but dangerous to reveal publicly. Detailed errors belong in server logs, where engineers can investigate them safely.

Question 25

What is the difference between a relational database and a NoSQL database?

Accepted Answer

A relational database stores data in tables with defined columns and relationships enforced through keys, and it is queried with SQL. NoSQL databases cover several models, including document, key-value, wide-column, and graph stores, and often favor flexible schemas and horizontal scaling. Relational systems are strong for consistent, connected data.

Question 26

What is a primary key, and why is it important?

Accepted Answer

A primary key is a column or set of columns that uniquely identifies each row in a table. It allows records to be referenced reliably, prevents duplicate entries, and gives the database an efficient way to locate rows. Foreign keys in other tables point back to primary keys to express relationships between records.

Question 27

Why do databases use indexes, and what do they cost?

Accepted Answer

Indexes are auxiliary structures that let the database find matching rows without scanning an entire table. They speed up reads on columns used in filters, joins, and sorting. The cost is extra storage and slower writes, because each insert or update must also maintain the index.

Question 28

What problem does database normalization aim to reduce or prevent?

Accepted Answer

Normalization organizes tables so that each fact is stored in one place, reducing redundancy. Redundant data invites inconsistency, since an update made in one copy may be missed in another. Splitting data into related tables, connected by keys, helps keep updates reliable. Over-normalizing can slow reads, so designers sometimes denormalize for performance.

Question 29

What is a database transaction, and what do ACID properties guarantee?

Accepted Answer

A transaction groups several database operations into a single unit that either completes entirely or has no effect. ACID stands for atomicity, consistency, isolation, and durability, which together keep data valid even when errors or concurrent users interfere. Transactions are essential for actions like moving money between accounts.

Question 30

How does an ORM help a developer, and what trade-off does it introduce?

Accepted Answer

An object-relational mapper translates between database tables and objects in application code, so developers can read and write records without hand-writing every SQL statement. This speeds development and reduces some injection risks when queries are parameterized. The trade-off is that generated queries can be inefficient, so developers must understand the SQL being produced.

Question 31

What is a schema migration, and why is it managed as code?

Accepted Answer

A schema migration is a versioned change to a database structure, such as adding a column or creating a table. Keeping migrations in version control lets every environment apply the same changes in the same order. This makes it easier to review changes, reproduce bugs, and roll back when a release fails.

Question 32

Why does an application need connection pooling for its database?

Accepted Answer

Opening a database connection takes time and resources, so creating a new one for every request would slow the application and can exhaust server limits. A connection pool keeps a set of open connections and lends them to requests as needed, then returns them for reuse.

Question 33

What is version control, and why does a team use Git?

Accepted Answer

Version control records every change to a project's files, allowing developers to review history, compare versions, and return to earlier states. Git is a distributed version control system in which each developer holds a full copy of the repository. Branches let people work on features in isolation before merging their changes back.

Question 34

What are the main steps in a continuous integration and deployment pipeline?

Accepted Answer

A typical pipeline begins when code is pushed to version control, then automatically builds the application and runs its tests. If those checks pass, the build is packaged and deployed to a staging environment for review. After approval, the same artifact is promoted to production, which reduces surprises from manual steps.

Question 35

What is the difference between a container and a virtual machine?

Accepted Answer

A virtual machine emulates an entire computer, including its own operating system kernel, on top of a hypervisor. A container packages an application with its dependencies and shares the host operating system kernel, so it starts faster and uses fewer resources.

Question 36

What is HTTPS, and what does TLS provide?

Accepted Answer

HTTPS is HTTP carried over Transport Layer Security, which encrypts traffic between the client and server. TLS also lets the client verify the server's identity through a certificate issued by a trusted authority. Together these protections keep passwords, cookies, and personal data from being read or altered in transit.

Question 37

What is cross-site scripting, and how do developers prevent it?

Accepted Answer

Cross-site scripting occurs when an attacker injects malicious script into a page that other users then run in their browsers. Developers prevent it by escaping untrusted output, validating input, and using templating systems that encode content by default. A Content Security Policy adds another layer by restricting which scripts a page may load.

Question 38

What is SQL injection, and what is the standard defense?

Accepted Answer

SQL injection happens when untrusted input is concatenated into a query, letting an attacker change the query's meaning. The standard defense is parameterized queries, which send the SQL structure and the data separately so input is never executed as code. Input validation and least-privilege database accounts add further protection.

Question 39

What is authentication, and how does it differ from authorization?

Accepted Answer

Authentication verifies who a user is, by checking a password, a token, or another credential. Authorization decides what that verified user is allowed to do, such as viewing an account or editing a record. A user can be correctly authenticated yet still denied access, so both checks must be enforced on the server.

Question 40

Why should secrets such as API keys never appear in frontend code?

Accepted Answer

Frontend code is delivered to the browser, where anyone can download and read it. Secrets placed in frontend code therefore lose their confidentiality immediately. Sensitive calls should be routed through a backend that holds the credentials securely and applies its own access checks.

Full Stack Web Development Flashcards

1How the Web Works

2Frontend Development

3Backend Services and APIs

4Databases and Data Modeling

5Deployment, Security, and Workflow

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