Full Stack Interview Questions and Answers- Part 10

Answer:

Docker is widely employed in software development and deployment for various reasons:

1. Isolation: It lets applications run in isolated units called containers, preventing conflicts and simplifying deployment.
2. Portability: Docker containers are consistent across different environments, ensuring uniform behavior from development to production.
3. Microservices: Docker is popular in microservices architectures, breaking applications into manageable units for easy scaling and maintenance.
4. CI/CD: It streamlines Continuous Integration and Continuous Deployment, ensuring consistent environments for testing and production.
5. Scaling: Docker containers can be scaled up or down swiftly to meet varying user demands.
6. Version Control: It facilitates versioning and rollbacks, simplifying the process of switching between different application versions.
7. Development & Testing: Docker ensures consistent environments for development and testing, reducing compatibility issues.
8. Resource Efficiency: Containers share the host OS kernel, making them lightweight and resource-efficient.

Answer:

To enhance web application loading speed, follow these practices

1. Image Optimization: Compress and optimize images to reduce their size while maintaining quality.
2. External CSS & JS: Keep CSS and JavaScript in external files for browser caching and smaller HTML files.
3. Minification: Remove unnecessary spaces and comments from HTML, CSS, and JS files.
4. Async Loading: Load CSS and JavaScript asynchronously to avoid blocking the rendering process.
5. Browser Caching: Set caching headers to store static resources locally, reducing future load times.
6. Content Delivery Network (CDN): Utilize CDNs to distribute content across multiple servers, decreasing server response time.
7. Reducing Redirects: Minimize redirects to prevent delays in page loading.
8. Server-Side Caching: Use caching techniques to store pre-rendered content on the server for quicker delivery.
9. GZIP Compression: Compress text-based resources with GZIP to reduce data transfer size.
10. Critical Rendering Path Optimization: Prioritize loading essential resources first for faster rendering.

Answer:

Blue-Green Deployment:

• Blue-Green Deployment involves maintaining two separate environments: blue (old version) and green (new version).
• Only one environment is live at a time, with the other being inactive.
• When deploying a new version, traffic is switched from the blue environment to the green environment.
• If any issues arise in the green environment, traffic can be switched back to the blue environment instantly.
• This approach ensures a quick rollback in case of issues with the new version.
• However, it requires a significant amount of resources to maintain both environments.
• Suitable for critical applications where downtime must be minimized.

Rolling Deployment:

• Rolling Deployment updates the existing environment incrementally.
• The new version is deployed to a subset of instances while others continue to serve traffic.
• The old version is gradually replaced by the new version, node by node or instance by instance.
• This method has a controlled impact on users, as only a portion of users are affected during deployment.
• It requires less resources compared to Blue-Green Deployment.
• Rollback can be complex if an issue arises during deployment.
• Suitable for applications with a lower tolerance for resource overhead and a less critical nature.

Answer:

Inversion of Control (IoC) is a design principle in software development that reverses the flow of control in a program. In traditional programming, a program controls the flow by directly calling functions or methods. With IoC, the control over execution flow is shifted to a container or framework that manages the dependencies and lifecycle of objects.

In the context of IoC:

• Objects are created and managed by an external entity (container).
• Dependencies are injected into objects rather than objects managing their own dependencies.
• The container controls the instantiation and destruction of objects.
• IoC reduces tight coupling between components, making the codebase more modular and maintainable.
• It enhances testability by allowing mock objects to be injected for testing purposes.
• IoC containers, like Spring in Java or Angular in TypeScript, manage object creation, dependency injection, and lifecycle management, adhering to the IoC principle.

Answer:

Referential Transparency in functional programming refers to the property of an expression where its value remains consistent regardless of its context or the order in which it’s evaluated. In other words, if an expression can be replaced with its value without changing the program’s behavior, it is considered referentially transparent.

Answer:

GET and POST are two HTTP methods used to send data to a web server:

Answer:

The Temporal Dead Zone (TDZ) in ECMAScript 6 (ES6) refers to the period between the creation of a variable using let or const and the point where the variable is assigned a value. During this phase, trying to access the variable results in a ReferenceError.

Answer:

A connection leak in Java occurs when database connections are not properly closed and returned to the connection pool after they are no longer needed. This can lead to a depletion of available connections in the pool, causing performance issues, delays, and even application crashes.

To fix connection leaks:

• Always Close Connections: Ensure that connections are closed explicitly using the .close() method or by employing try-with-resources or try-catch-finally blocks.
• Release Resources: Close any other resources associated with the connection, such as statements, result sets, and transactions.
• Connection Pooling: Use connection pooling libraries like Apache DBCP, HikariCP, or c3p0. These libraries handle connection creation, management, and recycling, minimizing the risk of leaks.
• Catch Exceptions: Employ proper exception handling to ensure that connections are closed even if an exception occurs.
• Automatic Resource Management: Utilize try-with-resources blocks to ensure that resources are automatically closed when they’re no longer needed.

Answer:

Event Bubbling and Event Capturing are two phases of event propagation in the DOM:

Event Bubbling: In this phase, an event starts from the target element that triggered it and travels up the DOM tree, passing through each ancestor element. This is the default behavior of event propagation.

Event Capturing (or Trickling): In this phase, the event is captured at the root element and then moves down the DOM tree through each descendant element until it reaches the target element. Event capturing is less common and is often explicitly enabled.

Answer:

To put it simply, “git pull” encompasses both “git fetch” and a subsequent “git merge.”

When you execute “git pull,” Git undertakes the task of automatically managing your updates. This process is context-sensitive, causing Git to merge the fetched commits directly into your active working branch. This automation, however, comes with a downside. It lacks the opportunity for you to review the changes before they are merged, potentially leading to complications if branch management isn’t meticulous.

On the other hand, “git fetch” involves collecting commits from a target branch that are absent in your current branch. These collected commits are stored in your local repository. Notably, these fetched commits remain independent of your current branch and are not merged automatically. This can be advantageous when you need to stay up-to-date with your repository without risking disruptions to your ongoing work. To blend these fetched commits into your master branch, a subsequent “git merge” operation is required.

Answer:

The fundamental distinction between REST and GraphQL lies in their approach to dealing with resources. REST revolves around dedicated resources, adhering to a structured API structure. In contrast, GraphQL adopts a more flexible perspective by treating everything as a connected graph. This allows GraphQL to be queried precisely for the needed data, without being confined to predefined resources.

Answer:

In Node.js, despite its single-threaded nature, concurrency is achieved through the concept of an event loop and callbacks. This is enabled by Node’s asynchronous APIs. The event loop, at the core of Node’s operation, monitors the completion of tasks and triggers corresponding events. These events, in turn, invoke listener functions, maintaining concurrency within the single thread.

Answer:

Clearing floats in CSS serves to ensure proper layout rendering. The CSS property “clear” determines whether an element can be positioned next to preceding floating elements or if it must be moved below them. By clearing floats, the containing element expands to accommodate its child elements correctly, avoiding layout glitches and unintended overlaps.

Answer:

Code sharing methodologies vary based on the JavaScript environment in use:

In a client-side (browser) environment, global variables/functions are accessible across scripts. Alternatively, Asynchronous Module Definition (AMD) with tools like RequireJS offers a modular approach.

For server-side (Node.js) scenarios, CommonJS is commonly employed. Each file is treated as a module, exporting variables/functions via the module.exports object.

ES2015 introduces a universal module syntax aiming to replace both AMD and CommonJS. This syntax is expected to be supported across both browser and Node environments, promoting consistent code sharing practices.

Answer:

Normalization: Normalization aims to eliminate data redundancy and inconsistency in database tables. It involves organizing data into separate tables and defining relationships between them to minimize duplication. The primary focus is on maintaining data integrity and reducing the chances of anomalies.

Denormalization: Denormalization involves intentionally introducing redundancy into the database design. It optimizes query performance by reducing the need for complex joins and improving data retrieval speed. While it may lead to some data redundancy and the potential for anomalies, denormalization is chosen when read-heavy operations are prioritized.

Answer:

A Closure is formed when a function accesses variables defined outside its own scope. It allows the function to retain access to those outer variables even after the outer function has finished executing. Here’s an example in JavaScript.

Answer:

An index is a database structure used to enhance the performance of data retrieval operations, especially in queries involving large datasets. It is created on one or more columns of a table and acts like a reference to the physical location of data rows in a table. Indexes allow the database management system to quickly locate the rows that match a certain condition specified in a query. They significantly reduce the need to scan the entire table for data retrieval, thus improving query speed and overall system performance. However, indexes do consume additional storage space and may slightly slow down data modification operations like inserts, updates, and deletes.

Answer:

In HTML5, data attributes are custom attributes that developers can define to store additional information within an HTML element. These attributes are prefixed with “data-” followed by a descriptive name. Data attributes allow developers to associate extra data with HTML elements without using non-standard attributes or altering the element’s content or appearance. They are particularly useful for scripting and styling purposes, as they provide a way to store data that can be accessed and manipulated using JavaScript or CSS.

For example, if you have an HTML element representing a product and you want to associate its unique identifier with it, you can use a data attribute like this: `div data-product-id=”123″ Product Name div`. This data can then be accessed using JavaScript to enhance interactivity without affecting the visual layout.

Answer:

Answer:

The Two-Phase Commit (2PC) is a mechanism in transaction processing systems that ensures data consistency and integrity across multiple distributed databases. It involves two distinct phases:

1. Prepare Phase: In this phase, the coordinator (a transaction manager) contacts all the participating databases (resource managers) and asks if they are ready to commit the transaction. Each database either agrees (votes “yes”) to commit or disagrees (votes “no”) based on its ability to commit the transaction.
2. Commit Phase: If all the participating databases agree to commit in the prepare phase, the coordinator sends a commit message to all the databases. This message instructs them to make the transaction permanent. If any database had voted “no” during the prepare phase, the coordinator sends an abort message, and all databases roll back the transaction.

The two-phase commit ensures that either all the participating databases commit the transaction or none of them do, thus maintaining data consistency. However, it introduces some performance overhead and potential bottlenecks due to the coordination required between the coordinator and the resource managers.