Advanced_enterprise_general

Question 1

What is n-tier (or multi-tier) architecture?

Answer 1

• N-tier architecture is a software design approach where an application is divided into multiple layers or tiers, each responsible for specific functions, such as presentation, business logic, and data access.

Question 2

What are microservices? Advantages and disadvantages?

Answer 2

• Microservices are a specific architectural style where a software system is built as a collection of separate services, each running as its own independent application. These services are designed to do specific tasks and communicate with each other through well-defined APIs, often over networks. Advantages include scalability and flexibility, while challenges may include complexity in management.

Question 3

What is Separation of Concerns?

Answer 3

• Separation of Concerns refers to the practice of breaking down the functionality of a software system into distinct and independent parts, often referred to as concerns. These concerns address specific aspects of the system’s behavior, like data storage, business logic, user interface, etc. Separation of concerns is a design principle that aims to make the codebase more manageable by isolating different responsibilities from each other.

Question 4

What is a layered design and why is it important in enterprise applications?

Answer 4

• Layered design organizes an application into distinct layers (e.g., presentation, business logic, data access). It improves maintainability, scalability, and enables changes to one layer without affecting others.

Question 5

What is Dependency Injection?

Answer 5

• Dependency Injection is a design pattern in which the components of a system receive their dependencies (e.g., services or objects) from external sources rather than creating them internally.

Question 6

What is the DAO pattern? When and how to implement?

Answer 6

• The DAO (Data Access Object) pattern separates data access logic from the rest of the application. It’s used to encapsulate interactions with a data source (e.g., a database). Implement it when you want to abstract data access and decouple it from the business logic.

Question 7

What is SOA? When to use?

Answer 7

• SOA (Service-Oriented Architecture) is an architectural style that focuses on organizing software as a collection of services that communicate with each other. Use SOA when you need modular, reusable, and loosely-coupled services in your system.

Question 8

What are unit test, integration test, system test, regression test, acceptance test? What is the major difference between these?

Answer 8

• Unit Test: Tests individual components or functions.
• Integration Test: Tests interactions between components.
• System Test: Tests the entire system.
• Regression Test: Ensures new changes don’t break existing functionality.
• Acceptance Test: Validates if the system meets the user’s requirements.

Question 9

What is code coverage? Why is it used? How you can measure?

Answer 9

• Code coverage measures the percentage of code that is executed during testing. It’s used to assess the thoroughness of testing. It’s measured using tools that analyze which parts of the code were executed during test runs.

Question 10

What does mocking mean? How would you do it ‘manually’ (i. e. without using any fancy framework)?

Answer 10

• Mocking involves creating simulated versions of objects or components to isolate the unit being tested. To do it manually, you’d create simple “fake” objects or functions that mimic the behavior of the real components without relying on external frameworks.

Question 11

What is a test case? What is an assertion? Give examples!

Answer 11

A test case is a specific scenario or condition you test to verify the behavior of a component. An assertion is a statement that checks whether the expected outcome of a test case matches the actual outcome. Example:
- Test case: Validate user login.
- Assertion: The user should be authenticated and directed to the dashboard.

Question 12

What is TDD? What are the benefits?

Answer 12

• TDD (Test-Driven Development) is a development approach where tests are written before the actual code. Benefits include improved code quality, faster development, and increased confidence in the system’s behavior.

Question 13

What are the unit testing best practices? (Eg. how many assertion should a test case contain?)

Answer 13

• Test a single unit (function or method) in isolation.
• Keep tests independent and isolated from each other.
• Test boundary conditions and edge cases.
• Use meaningful test names.
• Aim for one logical assertion per test case.

Question 14

What is arrange/act/assert pattern?

Answer 14

The Arrange-Act-Assert (AAA) pattern is a structure for writing unit tests.

• Arrange: Set up the test by initializing objects and preparing the environment.
• Act: Perform the action you’re testing.
• Assert: Verify that the action’s outcome matches the expected result.

Question 15

What is continuous integration? Why is CI important?

Answer 15

• Continuous Integration (CI) is the practice of frequently integrating code changes into a shared repository. It’s essential because it helps catch integration issues early, improves collaboration, and enables automated testing.

Question 16

Why are tests important in the CI workflow?

Answer 16

• Tests are crucial in the CI workflow because they ensure that code changes don’t introduce regressions or break existing functionality. Automated tests help catch issues before they reach production.

Question 17

Name some software that help the CI workflow!

Answer 17

• Popular CI/CD tools include Jenkins, Travis CI, CircleCI, GitLab CI/CD, and GitHub Actions.

Question 18

What is Continuous Delivery?

Answer 18

• Continuous Delivery is the practice of automatically deploying code changes to a staging or production environment after passing automated tests and reviews.

Question 19

What is Continuous Deployment?

Answer 19

• Continuous Deployment is an extension of Continuous Delivery where code changes are automatically deployed to production after passing tests without manual intervention.

Question 20

What is DevOps?

Answer 20

• DevOps is a set of practices, principles, and cultural philosophies that aim to improve collaboration and communication between development (Dev) and IT operations (Ops) teams in order to streamline and accelerate the software delivery lifecycle. The primary goal of DevOps is to enable organizations to deliver high-quality software more quickly, reliably, and efficiently.

Question 21

What kind of software-lifecycle models do you know?

Question 22

What is a UML diagram? What kind of diagram types do you know?

Answer 22

• UML (Unified Modeling Language) diagrams are visual representations used for designing and documenting software systems.
• I know class diagrams

Question 23

What is a UML class diagram? What are the typical elements?

Answer 23

• A UML class diagram shows the classes in a system and the relationships between them. Elements include classes, attributes, methods, associations, inheritance, and multiplicity.

Question 24

What kind of design patterns do you know? Bring at least 3 examples.

Answer 24

• Singleton
• Factory
• Observer
• Iterator

Question 25

What is the purpose of the Iterator Pattern?

Answer 25

• The Iterator Pattern provides a way to access elements of a collection without exposing its underlying representation, allowing traversal through the collection’s elements.

Question 26

What do you know about the SOLID principles?

Answer 26

SOLID is an acronym representing five design principles for creating maintainable and extensible software:

• Single Responsibility Principle (SRP)
• Open/Closed Principle (OCP)
• Liskov Substitution Principle (LSP)
• Interface Segregation Principle (ISP)
• Dependency Inversion Principle (DIP)

Question 27

How would you separate data storage code and business logic code (which uses stored data) in an application?

Answer 27

• Using design patterns like the Repository Pattern to encapsulate data storage code. The business logic should interact with the repository interface, allowing for flexible and testable data access while keeping it separate from the business logic.

Question 28

What is the difference between Stack and Queue data structure?

Answer 28

• Stack: A stack is a linear data structure that follows the Last In First Out (LIFO) principle. Elements are added and removed from the top.
• Queue: A queue is a linear data structure that follows the First In First Out (FIFO) principle. Elements are added at the rear (back) and removed from the front (head).

Question 29

What is a graph? What are simple graphs? What are directed graphs? What are weighted graphs?

Answer 29

• Graph: A graph is a collection of nodes (vertices) and edges that connect pairs of nodes. It’s used to represent relationships between different entities.
• Simple Graph: A simple graph is a graph where each pair of distinct nodes is connected by at most one edge.
• Directed Graph: In a directed graph (or digraph), edges have a direction, meaning they go from one node to another.
• Weighted Graph: A weighted graph assigns a weight or cost to each edge, representing some value associated with traversing that edge.

Question 30

What are trees? What are binary trees? What are binary search trees?

Answer 30

• Tree: A tree is a hierarchical data structure with a root node and subtrees of child nodes. It does not contain
  cycles.
• Binary Tree: A binary tree is a type of tree in which each node has at most two children, referred to as the
  left child and the right child.
• Binary Search Tree (BST): A binary search tree is a binary tree where for each node, all nodes in the left
  subtree have values less than the node’s value, and all nodes in the right subtree have values greater than the node’s value.

Question 31

How can you store graphs in programs? What are the advantages/disadvantages per each?

Answer 31

Graphs can be stored in programs using various data structures, including adjacency matrices (2D arrays), adjacency
lists (arrays/lists of neighbors for each node), and edge lists (list of edges).
- Advantages of Adjacency Matrix: Constant time to check if there’s an edge between two nodes. Suitable for dense graphs.
- Disadvantages of Adjacency Matrix: Consumes more memory for sparse graphs. Inefficient for large graphs.
- Advantages of Adjacency List: Efficient memory usage for sparse graphs. Faster for traversing neighbors.
- Disadvantages of Adjacency List: Slower edge existence checks compared to matrices.

Question 32

What are graph traversal algorithms? What is BFS, how does it work? What is DFS, how does it work?

Answer 32

Graph traversal algorithms are techniques used to systematically visit all the nodes or vertices of a graph, navigating through its edges according to a certain strategy.

• BFS (Breadth-First Search): BFS explores all nodes at the current depth level before moving to the next level. It uses a queue data structure.
• DFS (Depth-First Search): DFS explores as far as possible along one branch before backtracking. It uses a stack (or recursion).

Question 33

How does dictionary work?

Answer 33

• A dictionary, often referred to as a hashmap or associative array, is a data structure that stores key-value pairs. It uses a hash function to map keys to indices in an underlying array, allowing for efficient retrieval and storage of values based on their keys.

Question 34

Why is it important for keys in a hashmap to have an immutable type? (Consider string for example.)

Answer 34

• Immutable keys are important in a hashmap to ensure the stability of the key’s hash value. If the key could change after being inserted, the hashmap could lose track of the value’s location, making retrieval impossible. Immutable keys guarantee that the hash value remains consistent.

Question 35

What is QuickSort? Describe the main logic of this sorting algorithm.

Answer 35

• QuickSort is a popular sorting algorithm that follows the divide-and-conquer strategy:

1. Choose a pivot element.
2. Partition the array into two subarrays: elements less than the pivot and elements greater than the pivot.
3. Recursively sort the subarrays.
4. Combine the sorted subarrays and the pivot to get the final sorted array.

Question 36

What is OAuth2?

Answer 36

• OAuth2 is an authorization framework that allows third-party applications to access a user’s data without exposing their credentials. It provides a secure way for users to grant limited access to their resources on one site (resource server) to another site (client application).

Question 37

What is Basic Authentication?

Answer 37

• Basic Authentication is a simple authentication mechanism where the user’s credentials (username and password) are encoded and sent as a header in each request. It’s not very secure on its own, as credentials can be easily intercepted.

Question 38

What is CORS, why it’s needed in browsers?

Answer 38

• CORS is a security feature implemented by web browsers to control which origins are allowed to access resources from a different origin. It prevents unauthorized cross-origin requests, thus enhancing web security.

Question 39

How can you initialize a CSRF attack?

Answer 39

• CSRF is an attack where a malicious website tricks a user’s browser into making an unintended request to a different site where the user is authenticated. This can lead to unauthorized actions being performed on the victim’s behalf.

Question 40

What is JWT used for? Where to store it on client side?

Answer 40

• JWT is a compact, URL-safe means of representing claims between two parties. It’s often used for authentication and information exchange. JWTs can be stored on the client side, typically in cookies or local storage.

Question 41

When do you need to use threads in an application?

Answer 41

• Threads are used in applications to achieve concurrent execution of tasks, allowing multiple parts of a program to run simultaneously and improve overall performance and responsiveness.

Question 42

What is a daemon thread?

Answer 42

• A daemon thread is a thread that runs in the background, providing services to other threads without preventing the program from exiting if only daemon threads are running.

Question 43

What is the difference between concurrent and parallel execution of code?

Answer 43

• Concurrent Execution: Multiple tasks are being executed in overlapping time intervals, but not necessarily simultaneously.
• Parallel Execution: Multiple tasks are executed simultaneously, often utilizing multiple processors or cores.

Question 44

What is the most important problem developers are faced when using threads?

Answer 44

• The most important challenge when using threads is ensuring proper synchronization and coordination to avoid issues like data races, deadlocks, and inconsistent states.

Question 45

In what kind of situations can deadlocks occur?

Answer 45

• Deadlocks occur when two or more threads are unable to proceed because each is waiting for the other to release a resource.

Question 46

What are possible ways to prevent deadlocks from occurring?

Answer 46

• Using a single lock hierarchy.
• Employing timeouts for acquiring locks.
• Using deadlock detection algorithms.

Question 47

What does critical section or critical region mean in the context of concurrent programming?

Answer 47

• A critical section (or critical region) is a part of the code where shared resources are accessed, and only one thread should access it at a time. Proper synchronization mechanisms are used to ensure mutual exclusion and prevent data corruption.