How can LIMIT and OFFSET be used effectively to optimize SQL queries?
- Use LIMIT to specify the maximum number of rows to retrieve and OFFSET to skip a certain number of rows.
- Use OFFSET to specify the maximum number of rows to retrieve and LIMIT to skip a certain number of rows.
- Use LIMIT and OFFSET together to retrieve all rows in a table.
- Use LIMIT and OFFSET to restrict the number of columns retrieved in a query.
LIMIT is used to restrict the number of rows in the result set, while OFFSET is used to skip a certain number of rows. This is helpful for paginating results and optimizing queries when you don't need to retrieve the entire dataset.
Which of the following strategies can be used to efficiently serve static assets and optimize performance?
- Caching static assets at the server-side.
- Using long, descriptive file names for static assets.
- Serving static assets through a Content Delivery Network (CDN).
- Storing static assets in a database.
Serving static assets through a Content Delivery Network (CDN) is an efficient strategy to optimize performance by distributing assets across geographically distributed servers, reducing latency and improving load times. The other options either don't directly address performance optimization or provide incorrect methods.
What does JWT stand for in the context of web security?
- JavaScript Web Token
- JSON Web Token
- JavaScript Web Transfer
- JSON Web Transfer
JWT stands for JSON Web Token. It is a compact, self-contained means for securely transmitting information between parties as a JSON object. JWTs are commonly used for authentication and authorization in web security. The other options are not accurate acronyms for JWT.
Why is it important to define the correct path for serving static files in Express.js?
- To improve security by hiding static files.
- To enhance performance by reducing load times.
- To avoid conflicts with route handling.
- To simplify the code structure.
Defining the correct path for serving static files in Express.js is important to avoid conflicts with route handling. If the path is not specified correctly, Express.js might mistakenly interpret a URL as a route, leading to unexpected behavior. The other options, while important, are not the primary reason for specifying the correct static file path.
You are designing a microservices architecture where different services need to access shared data. How would you implement caching to ensure data consistency across services?
- Distributed Caching
- Local Caching
- Centralized Database
- Data Replication
In a microservices architecture with shared data, Distributed Caching would be the ideal choice. Distributed caches ensure data consistency across services by replicating data across multiple cache nodes, making it accessible to all services while maintaining data integrity. Local Caching is limited to individual services, and Centralized Databases may introduce bottlenecks and fail to ensure data consistency. Data Replication can be complex and is not a direct caching strategy.
In JavaScript, the Symbol data type was introduced in ________.
- ECMAScript 2015 (ES6)
- JavaScript 1.5
- Node.js v10
- ESNext
The Symbol data type was introduced in ECMAScript 2015 (ES6). It allows you to create unique and immutable values that can be used as object property keys.
In Express.js, middleware functions have access to the request object, the response object, and the ______ function.
- next()
- send()
- app()
- router()
In Express.js, middleware functions have access to the request object (req), the response object (res), and a callback function commonly named next(). The next() function is used to pass control to the next middleware function in the chain.
Which of the following is the primary goal of input sanitization?
- Enhancing user experience.
- Ensuring data accuracy.
- Preventing cross-site scripting (XSS) attacks.
- Optimizing database performance.
The primary goal of input sanitization is to prevent cross-site scripting (XSS) attacks. It involves removing or encoding potentially dangerous characters from user input to ensure that it cannot be executed as script on a web page, thus enhancing web security.
Which of the following is an example of an Object Document Mapper (ODM) for MongoDB in Node.js?
- Mongoose
- Sequelize
- Knex
- TypeORM
Mongoose is a popular Object Document Mapper (ODM) for MongoDB in Node.js. It provides a structured way to interact with MongoDB, allowing developers to define schemas and models for their data. The other options, Sequelize, Knex, and TypeORM, are primarily used with relational databases and are not ODMs for MongoDB.
When dealing with CORS, the Access-Control-Allow-Credentials header should be set to true to allow ________ to be included in the request.
- cookies
- headers
- authentication
- origins
When dealing with CORS, the Access-Control-Allow-Credentials header should be set to true to allow cookies to be included in cross-origin requests. This is necessary when you want to make authenticated requests across origins.