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.
You are developing a Node.js library intended to be used as a dependency in other projects. How would you utilize the package.json and package-lock.json files to ensure that the consumers of your library do not face any versioning or dependency conflicts?
- Do not provide a package-lock.json file with your library
- Specify the exact versions of dependencies in your package.json
- Use wildcard (*) versions for dependencies in your package.json
- Ask consumers to manually update your library's dependencies
To ensure consumers do not face versioning or dependency conflicts, you should specify the exact versions of dependencies in your package.json. This guarantees that consumers get the same dependencies you tested with. Option 1 is not recommended, and options 3 and 4 can lead to conflicts and issues.
In Node.js, '______' is used to signify the end of a writable stream.
- finish
- close
- end
- complete
In Node.js, the 'end' event is used to signify the end of a writable stream. This event is emitted when all data has been written to the stream and it's safe to end it. The other options (finish, close, complete) are not typically used for this purpose.
Why is caching used in web applications?
- To reduce server load and improve performance
- To increase server load and slow down performance
- To secure user data
- To display error messages
Caching in web applications is used to reduce server load and improve performance by storing frequently accessed data, such as web pages or database query results, so that it can be quickly retrieved without the need to regenerate it. Caching helps in minimizing the need for redundant processing and data retrieval.
In semantic versioning, what does a change in the 'patch' version (e.g. 1.2.3) typically indicate?
- Bug fixes
- New features
- Backwards-incompatible changes
- Minor improvements
In SemVer, a change in the 'patch' version indicates that there have been backwards-compatible bug fixes. This means that the changes made in this version should not break existing functionality and are intended to address issues and improve stability.
You are working on a web scraping tool. You have multiple URLs to fetch data from, but you want to proceed with the next steps only when data from all URLs are fetched successfully. How would you achieve this using Promises?
- Use Promise.all()
- Use Promise.race()
- Use async/await without Promise.all()
- Use multiple then() blocks
To proceed with the next steps only when data from all URLs is fetched successfully, you should use Promise.all(). This method takes an array of Promises and resolves only when all of them resolve successfully. Promise.race() resolves on the first success, which is not suitable for this scenario. Using async/await without Promise.all() may not ensure that all URLs are successfully fetched before proceeding.