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 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.
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.
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.
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.
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.
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.
How does the try...catch statement work in asynchronous operations in Node.js?
- It cannot be used with asynchronous operations.
- It catches exceptions asynchronously with the help of callbacks.
- It works synchronously and blocks the event loop.
- It is only applicable to synchronous code.
In Node.js, the try...catch statement can be used with asynchronous operations, but it doesn't catch exceptions directly in asynchronous callbacks. Instead, it catches exceptions that occur during the setup of asynchronous operations or in the main event loop. It doesn't block the event loop.
How does denormalization in database schema design affect data redundancy and read performance?
- Decreases data redundancy and improves read performance
- Increases data redundancy and improves read performance
- Decreases data redundancy and decreases read performance
- Increases data redundancy and decreases read performance
Denormalization in database schema design increases data redundancy but can improve read performance. By storing redundant data, queries can often be faster since they require fewer joins. However, this comes at the cost of increased storage requirements and potential data update anomalies.
To handle HTTP POST requests in Express, you would use the ______ method.
- GET
- POST
- PUT
- DELETE
To handle HTTP POST requests in Express, you would use the POST method. The POST method is used for submitting data to be processed to a specified resource.
How can developers handle multiple callback functions to avoid "Callback Hell" in Node.js?
- Nest callbacks within each other for better organization.
- Use async/await to write asynchronous code more sequentially.
- Avoid callbacks altogether and use Promises exclusively.
- Increase the event loop's capacity for handling callbacks.
To avoid "Callback Hell" in Node.js, developers can use async/await, which allows them to write asynchronous code in a more sequential and readable manner. This approach reduces the nesting of callbacks and makes the code easier to maintain.
You are developing a system with stringent data integrity requirements. How would you design the schema to enforce data integrity constraints and handle violations effectively?
- Use database triggers to enforce constraints.
- Implement application-level validation only.
- Apply foreign key constraints to maintain data relationships.
- Rely solely on user input validation.
Option (1) is a valid approach using database triggers to enforce constraints. Option (2) shouldn't be the sole method, as application-level validation can be bypassed. Option (3) is essential, especially for maintaining data relationships. Option (4) is not sufficient for ensuring data integrity on its own.