30+ Amazon Interview Questions and Answers

I am currently working on a web application for a retail company using React, Node.js, and MongoDB.

• Developing a responsive UI using React and Redux

• Implementing server-side logic using Node.js and Express

• Storing and retrieving data using MongoDB

• Integrating third-party APIs for payment processing and shipping

• Writing automated tests using Jest and Enzyme

Dependency Injection is a design pattern used to remove hard-coded dependencies and make code more flexible and testable.

• Dependency Injection is implemented by injecting the required dependencies into a class rather than creating them within the class.

• This can be achieved through constructor injection, setter injection, or interface injection.

• For example, in Java, Spring Framework provides a powerful dependency injection mechanism through its @Autowired annotation.

• Dependency ...read more

Yes, authentication is implemented using OAuth 2.0 protocol.

• OAuth 2.0 protocol is used for authentication.

• Access tokens are issued to authorized clients.

• Refresh tokens are used to obtain new access tokens.

• Authentication is required for all API endpoints.

Ref and out are keywords used in C# to pass arguments by reference instead of value.

• Ref and out are used to pass arguments by reference instead of value

• Ref keyword is used to pass a reference of the variable to the method

• Out keyword is used to pass a reference of the variable to the method and requires the variable to be initialized before use

• Ref keyword can be used to modify the value of the variable passed as an argument

• Out keyword is used when the method needs to return mu...read more

Interfaces define contracts for behavior while abstract classes provide partial implementation.

• Interfaces cannot have implementation while abstract classes can have partial implementation.

• A class can implement multiple interfaces but can inherit from only one abstract class.

• Interfaces are used for loose coupling while abstract classes are used for code reuse.

• Example: An interface 'Drawable' can define a method 'draw' which any class implementing it must define. An abstract cl...read more

Value types hold the data directly, while reference types hold a reference to the data.

• Value types are stored on the stack, while reference types are stored on the heap.

• String is a reference type in .NET.

• Value types include int, float, and bool.

• Reference types include arrays, classes, and interfaces.

Self Join is a way to join a table with itself using aliases.

• It is useful when we need to compare records within the same table.

• It requires the use of aliases to differentiate between the two instances of the same table.

• Example: SELECT a.name, b.name FROM employees a, employees b WHERE a.manager_id = b.employee_id;

Action Filters are attributes that can be applied to controller actions to perform pre/post processing.

• Action Filters are used to modify the behavior of controller actions.

• They can be used to perform authentication, logging, caching, etc.

• Action Filters can be applied globally or to specific actions.

• Examples include [Authorize] for authentication and [OutputCache] for caching.

• Action Filters can also be created by the developer to perform custom processing.

Interfaces are a way to define a contract between two objects, specifying the methods and properties that one object must implement.

• Interfaces allow for loose coupling between objects, making it easier to change the implementation of one object without affecting others.

• They promote code reusability by allowing multiple objects to implement the same interface.

• Interfaces can be used to create mock objects for testing purposes.

• Examples of interfaces in Java include Comparable, R...read more

Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity.

• Normalization involves breaking down a table into smaller tables and defining relationships between them.

• There are different levels of normalization, with each level reducing redundancy and improving data integrity further.

• Normalization helps to prevent data inconsistencies and anomalies, and makes it easier to maintain and update the database.

• Examples of normalizatio...read more

Delegates are a type-safe function pointer used to encapsulate a method.

• Delegates allow methods to be passed as parameters to other methods.

• They can be used to implement callbacks and event handlers.

• Delegates can be chained together to create a pipeline of method calls.

• They are commonly used in .NET framework for event handling and LINQ queries.

Shallow copy creates a new object with same values as original, but references the same memory locations.

• Shallow copy only copies the top-level object, not the nested objects.

• Changes made to the original object will reflect in the copied object.

• Use MemberwiseClone() method to create shallow copy of an object.

• Example: int[] arr1 = {1, 2, 3}; int[] arr2 = arr1.Clone() as int[]; arr2[0] = 4; Console.WriteLine(arr1[0]); // Output: 1

Overriding is when a subclass provides its own implementation of a method from the superclass, while overloading is when a class has multiple methods with the same name but different parameters.

• Overriding is used to provide a specific implementation of a method in a subclass that is already defined in the superclass.

• Overloading is used to define multiple methods with the same name but different parameters in a class.

• Overriding is used for runtime polymorphism, while overloadi...read more

IEnumerable is in-memory collection while IQueryable is a queryable data source.

• IEnumerable is used for querying data from in-memory collections like List, Array, etc.

• IQueryable is used for querying data from a data source like a database.

• IEnumerable executes the query on the client-side while IQueryable executes the query on the server-side.

• IQueryable is more efficient when working with large datasets as it allows for filtering and sorting on the server-side.

• Example: var lis...read more

String is immutable while StringBuilder is mutable.

• String is a final class and its value cannot be changed once created.

• StringBuilder is a mutable class and its value can be changed without creating a new object.

• String concatenation creates a new String object each time, while StringBuilder is more efficient for concatenation.

• Use String for fixed values and StringBuilder for dynamic values.

Optimize select statements by using indexes, avoiding unnecessary joins, and limiting the number of columns selected.

• Use indexes to speed up queries

• Avoid unnecessary joins and subqueries

• Limit the number of columns selected

• Use WHERE clauses to filter results

• Use GROUP BY and ORDER BY clauses wisely

• Consider using stored procedures or views

• Regularly analyze and optimize the database

Indexing is a technique to improve database performance by reducing the time taken to retrieve data.

• Indexes are created on one or more columns of a table.

• Types of indexes include clustered, non-clustered, unique, and full-text indexes.

• Clustered indexes determine the physical order of data in a table.

• Non-clustered indexes are separate structures that contain a copy of the indexed columns and a pointer to the actual data.

• Unique indexes ensure that each value in the indexed colu...read more

IAM role is used to grant permissions to AWS services, while IAM user is used to grant permissions to individuals.

• IAM role is used to delegate access to AWS services, such as EC2 instances or Lambda functions

• IAM user is used to grant permissions to individuals who need to interact with AWS resources

• IAM roles do not have long-term credentials like IAM users, instead they are assumed by trusted entities

• IAM users have their own set of security credentials (access key, secret key...read more

Joins are used to combine data from two or more tables based on a related column. A view is a virtual table created from a query.

• Joins are used to retrieve data from multiple tables based on a related column

• There are different types of joins such as inner join, left join, right join, and full outer join

• Views are virtual tables created from a query that can be used to simplify complex queries or restrict access to sensitive data

• Views do not store data themselves, but rather pr...read more

Load balancer distributes incoming network traffic across multiple servers, while autoscaling group automatically adjusts the number of instances based on traffic.

• Load balancer distributes traffic evenly across multiple servers to improve performance and reliability

• Autoscaling group automatically adjusts the number of instances based on traffic demand

• IAM role defines a set of permissions for AWS resources, while IAM user is an entity that can interact with AWS services

• IAM rol...read more

Promises in JavaScript are used to handle asynchronous operations and avoid callback hell.

• Promises represent a value that may not be available yet but will be resolved at some point in the future.

• They have three states: pending, fulfilled, or rejected.

• Promises can be chained using .then() and .catch() methods.

• They can also be used with async/await syntax.

• Example: new Promise((resolve, reject) => {...}).then(result => {...}).catch(error => {...})

IIFE stands for Immediately Invoked Function Expression. It is a function that is executed as soon as it is defined.

• IIFE is enclosed in parentheses () to make it an expression.

• It is followed by another set of parentheses () to invoke the function immediately.

• It is commonly used to create a private scope for variables and functions.

• Example: (function() { console.log('Hello World!'); })();

Phase 1 establishes secure communication channel, Phase 2 sets up secure data transfer within the channel.

• Phase 1 negotiates security parameters and establishes a secure channel between two IPsec peers.

• Phase 2 sets up secure data transfer within the established secure channel.

• Phase 1 uses ISAKMP (Internet Security Association and Key Management Protocol) for key exchange.

• Phase 2 uses IPsec protocols like ESP (Encapsulating Security Payload) or AH (Authentication Header) for s...read more

Stored procedures are pre-written SQL codes that can be saved and reused in a database.

• Stored procedures are used to improve database performance and security.

• They can be called from within an application or directly from the database.

• They can accept input parameters and return output parameters or result sets.

• Examples include procedures for inserting, updating, and deleting data.

• They can also be used for complex data manipulation and business logic.

Manifest files in k8 are configuration files used to define the desired state of resources in a Kubernetes cluster.

• Manifest files are written in YAML or JSON format.

• They define the resources like pods, services, deployments, etc., that should be created in the cluster.

• Manifest files can be applied using kubectl apply command.

• They help in maintaining the desired state of the cluster and managing configurations.

• Example: a pod manifest file may define the container image, ports,...read more

ER circuit is a dedicated point-to-point connection while IPsec tunnel is a secure virtual private network connection over the internet.

• ER circuit is a physical connection between two locations, typically provided by a telecom provider.

• IPsec tunnel is a secure encrypted connection over the internet, often used for connecting remote offices or users.

• ER circuit offers dedicated bandwidth and low latency, suitable for high-priority traffic.

• IPsec tunnel provides secure communicat...read more

Tf state file is a JSON file that stores the current state of your infrastructure managed by Terraform.

• Contains information about resources, their attributes, and dependencies

• Used by Terraform to keep track of the infrastructure state

• Should be stored securely and not shared publicly

Reducing latency involves optimizing network infrastructure, minimizing data transfer distances, and utilizing caching techniques.

• Optimize network infrastructure by using faster hardware and reducing network congestion

• Minimize data transfer distances by using content delivery networks (CDNs) and edge computing

• Utilize caching techniques to store frequently accessed data closer to the end user

• Implementing load balancing to distribute network traffic efficiently

Application gateway is a load balancer that manages traffic to web applications.

• Acts as a reverse proxy to distribute incoming traffic across multiple servers

• Provides SSL termination, URL-based routing, and session persistence

• Can perform application layer (HTTP) load balancing

• Supports WAF (Web Application Firewall) for enhanced security

AWS Config is a service that provides a detailed inventory of AWS resources and configuration settings.

• AWS Config continuously monitors and records configurations of AWS resources.

• It helps assess, audit, and evaluate the configurations for compliance.

• AWS Config can be used to track changes to resources over time.

• It provides a history of resource configuration changes for troubleshooting and security analysis.

SSL authentication involves multiple steps to verify the identity of the server and establish a secure connection.

• Client sends a request to the server over HTTPS

• Server responds with its SSL certificate

• Client verifies the certificate's authenticity using a trusted CA

• Client generates a session key and encrypts it with the server's public key

• Server decrypts the session key using its private key

• Client and server can now communicate securely using the session key

Load balancer distributes incoming network traffic across multiple servers to ensure no single server is overwhelmed.

• Distributes traffic evenly across servers

• Improves reliability and scalability

• Can be hardware-based or software-based

• Examples: F5 BIG-IP, NGINX, HAProxy