Authentication, Databases, Performance & Scaling, System Design & Architecture, Node.js & Security, Database Mastery (ACID & Optimization), Frontend & React, React Performance & Advanced Hooks

Flashcards covering key vocabulary related to authentication and database concepts.

Authentication

The process of verifying who a user is.

Authorization

Determines what an authenticated user can do.

JWT (JSON Web Token)

A secure ID card used to identify users across web applications.

Access Token

A temporary token with a short lifespan, used for API requests.

Refresh Token

A long-lived token used to obtain a new access token when the original expires.

Sessions

Stateful method where the server remembers user data.

Cookies

Small pieces of data stored on the user's computer by the browser.

Bcrypt

A one-way function used to hash passwords.

SQL

Structured Query Language; used for databases with strict schema.

NoSQL

A flexible, document-based database format (like MongoDB) for unstructured data.

N+1 Query Problem

An issue that arises when a single query results in multiple subsequent queries to the database.

Joins

A method to combine records from two or more tables in a database.

ACID properties

A set of properties (Atomicity, Consistency, Isolation, Durability) ensuring reliable database transactions.

Caching

A technique to store frequently accessed data in a faster storage (like RAM) for quick access.

TTL

Stands for Time to Live; the expiration date for cached data to prevent it from staying forever.

CDN

Content Delivery Network; servers located geographically to store images/videos closer to users and reduce lag.

CAP Theorem

A principle in distributed systems stating you can only choose two of the following: Consistency, Availability, or Partition Tolerance.

Consistency (C)

A property wherein all users see the exact same data at the same time.

Availability (A)

A property ensuring the system always responds to requests, even with slightly outdated data.

Partition Tolerance (P)

A requirement for a system to continue operating despite network failures.

Message Queues

A method of offloading slow tasks to background workers so that users do not experience delays.

RabbitMQ/Kafka

Examples of message queue systems that help manage background processing of tasks.

Queue

A data structure where tasks wait to be processed by background workers.

Vertical Scaling

Increasing the resources of a single server (e.g., more RAM, CPU power) to handle more load.

Horizontal Scaling

Adding more servers to distribute the load; essential for handling large-scale applications.

Load Balancer

A device or software that distributes network or application traffic across multiple servers to ensure no single server is overwhelmed.

Monolith

A software architecture where all components are interconnected and interdependent, making it easy to deploy but hard to scale.

Microservices

An architectural style that structures an application as a collection of small, loosely coupled services, enhancing modularity and scalability.

MVC Pattern (Model-View-Controller)

A software design pattern that separates an application into three main logical components: Model (data), View (UI), and Controller (business logic).

Node.js Runtime

A JavaScript runtime built on Chrome's V8 JavaScript engine.

Single-Threaded

Node.js has a single main thread that handles all requests.

Non-blocking I/O

A method of processing input/output that allows the server to continue executing other tasks without waiting for operations to complete.

Event Loop

The mechanism that manages asynchronous tasks in Node.js, enabling the main thread to remain non-blocked.

Async/Await

A syntax in JavaScript that allows asynchronous code to be written in a synchronous manner, improving code readability.

SQL Injection (SQLi)

A type of attack where an attacker inserts malicious SQL code into a database query to manipulate the database.

Parameterized Queries

A method of using templates for database queries that treat inputs as data rather than executable code.

XSS (Cross-Site Scripting)

An attack that injects malicious scripts into web pages understood by users' browsers to steal information such as cookies.

CSRF (Cross-Site Request Forgery)

An attack that tricks a user's browser into making unwanted requests to a web application in which they are authenticated.

CSRF Tokens

Unique keys used to validate that a request originated from an authenticated user's site.

Environment Variables (.env)

Files used to store configuration settings, such as API keys and database passwords, separate from your codebase.

Atomicity

The property ensuring that a transaction is either fully completed or not executed at all; if part of a transaction fails, the entire transaction fails.

Consistency

The principle that a database must always transition from one valid state to another, adhering to all predefined rules and constraints.

Isolation

The ability of concurrent transactions to operate independently without interference, ensuring each transaction's operations remain unaffected by others.

Durability

The guarantee that once a transaction has been committed, it will remain so, even in the event of a system failure.

Indexing

A data structure that improves the speed of data retrieval operations on a database table, enabling quick lookup without scanning rows.

N+1 Query Problem

An inefficiency that occurs when a single query results in multiple subsequent queries, which can be mitigated using Joins or Eager Loading.

One-to-Many Relationship

A type of data relationship where one record in a table is associated with multiple records in another table, such as a user with many posts.

Many-to-Many Relationship

A relationship where multiple records in one table can be associated with multiple records in another table, such as students enrolled in various courses.

Inner Join

A database operation that returns only the rows where there is a match in both tables provided in the query.

Left Join

A database operation that returns all rows from the left table and matched rows from the right table; if there is no match, NULLs are displayed for the right table.

let vs const

Use const by default; use let only if the value will change.

Arrow Functions

A shorter syntax for functions, e.g., () => {}.

Destructuring

Method to pull values out of objects or arrays easily, e.g., const { name } = user.

Components in React

Reusable building blocks of the UI that define how a part of the interface should appear.

Props in React

Data passed down from parent components to child components; they are read-only.

State in React

Data managed inside a component that can change over time, influencing the component's rendering.

Virtual DOM

A lightweight copy of the real DOM that React uses to detect changes efficiently before updating the real DOM.

useState Hook

A Hook that lets functional components manage state.

useEffect Hook

Handles side effects in components, such as data fetching or timers, and runs after the component renders.

useContextHook

Avoids prop drilling by sharing data globally across components.

Re-render Problem

Occurs each time state changes, causing lag if components are heavy.

Memoization

Caching technique used in React to prevent unnecessary re-renders.

React.memo

A higher-order component that prevents re-renders unless props change.

useMemo

A hook that caches the result of an expensive calculation.

useCallback

A hook that caches a function to prevent child components from re-rendering.

CSR (Client-Side Rendering)

A rendering strategy where the browser downloads a blank page and JavaScript constructs the page.

SSR (Server-Side Rendering)

A rendering strategy where the server builds HTML for each request, benefiting SEO.

SSG (Static Site Generation)

A rendering strategy where the page is built once at compile time, resulting in faster load times.