AWS Interview Questions

This section provides AWS Interview Questions.

Basic Level

  1. What is AWS?

    • Answer: AWS (Amazon Web Services) is a comprehensive cloud computing platform provided by Amazon. It offers a wide range of cloud services such as computing power, storage options, networking, and databases, enabling businesses to build scalable and reliable applications.

  2. What are the core services provided by AWS?

    • Answer: The core AWS services include:
      • EC2 (Elastic Compute Cloud): Provides scalable computing capacity.
      • S3 (Simple Storage Service): Object storage service for data backup, archiving, and analytics.
      • RDS (Relational Database Service): Managed relational database service.
      • Lambda: Serverless computing service that automatically runs your code in response to events.

  3. What is an EC2 instance?

    • Answer: An EC2 instance is a virtual server in Amazon's Elastic Compute Cloud (EC2) that allows you to run applications on the AWS infrastructure. Instances can be launched with different configurations based on computing needs.

  4. What are the different types of EC2 instances?

    • Answer: EC2 instances are categorized into several types:
      • General Purpose: Balanced compute, memory, and networking (e.g., t3, m5).
      • Compute Optimized: Ideal for compute-bound applications (e.g., c5).
      • Memory Optimized: Designed for memory-intensive tasks (e.g., r5).
      • Storage Optimized: Optimized for high-performance storage (e.g., i3).

  5. What is Amazon S3?

    • Answer: Amazon S3 (Simple Storage Service) is an object storage service that allows users to store and retrieve any amount of data at any time. It's commonly used for backup, archiving, content distribution, and data lakes.

  6. How does Amazon S3 ensure data durability?

    • Answer: Amazon S3 is designed for 99.999999999% (11 nines) of data durability by automatically replicating your data across multiple Availability Zones (AZs) within a region.

  7. What is the difference between public and private subnets in a VPC?

    • Answer: A public subnet is one that has a route to an internet gateway, allowing instances in this subnet to access the internet. A private subnet does not have direct access to the internet and is typically used for instances that should not be publicly accessible.

  8. What is AWS Lambda?

    • Answer: AWS Lambda is a serverless computing service that runs your code in response to events and automatically manages the compute resources. It allows you to execute code without provisioning or managing servers.

  9. What is an IAM role?

    • Answer: An IAM (Identity and Access Management) role is a set of permissions that define what actions an AWS resource or service can perform. Roles are used to delegate permissions to users, applications, or services within AWS.

  10. How does Elastic Load Balancing (ELB) work?

    • Answer: Elastic Load Balancing (ELB) automatically distributes incoming application traffic across multiple EC2 instances, containers, or IP addresses in one or more Availability Zones. This ensures that no single instance bears too much load, enhancing fault tolerance and availability.

Intermediate Level

  1. What is the difference between scaling up and scaling out in AWS?

    • Answer: Scaling up (vertical scaling) involves increasing the size of an existing resource (e.g., upgrading an EC2 instance type). Scaling out (horizontal scaling) involves adding more instances to handle increased load, distributing the traffic across multiple resources.

  2. What is an Elastic IP address?

    • Answer: An Elastic IP address is a static, public IPv4 address that you can associate with your AWS account and assign to instances in your VPC. It allows you to mask the failure of an instance by remapping the address to another instance.

  3. How can you secure data at rest in AWS?

    • Answer: You can secure data at rest in AWS using encryption. AWS offers several methods:
      • Server-Side Encryption (SSE): AWS encrypts data on your behalf as it writes it to disk (e.g., SSE-S3, SSE-KMS).
      • Client-Side Encryption: Data is encrypted before sending it to AWS.
      • AWS Key Management Service (KMS): Manages cryptographic keys for encryption.

  4. What is Amazon RDS, and what are its benefits?

    • Answer: Amazon RDS (Relational Database Service) is a managed service that simplifies the setup, operation, and scaling of a relational database in the cloud. Benefits include automated backups, software patching, scaling, and replication.

  5. What is the difference between RDS and DynamoDB?

    • Answer: RDS is a managed relational database service supporting SQL databases (e.g., MySQL, PostgreSQL). DynamoDB is a managed NoSQL database service that provides high availability and performance for key-value and document data models.

  6. How does AWS CloudFront work?

    • Answer: AWS CloudFront is a content delivery network (CDN) that speeds up the delivery of your content (e.g., websites, videos) by caching copies at edge locations globally. It routes requests to the nearest edge location to reduce latency.

  7. What is an Auto Scaling group?

    • Answer: An Auto Scaling group is a collection of EC2 instances that are automatically scaled in or out based on defined criteria, such as CPU utilization or request rates, to handle varying levels of traffic and maintain application availability.

  8. How do you implement high availability in AWS?

    • Answer: High availability can be implemented by:
      • Deploying resources across multiple Availability Zones.
      • Using Elastic Load Balancers to distribute traffic.
      • Configuring Auto Scaling groups for automated scaling.
      • Setting up Multi-AZ deployments for databases.

  9. What are Security Groups and Network ACLs?

    • Answer: Security Groups are virtual firewalls that control inbound and outbound traffic to individual instances within a VPC. Network ACLs are stateless and control traffic at the subnet level, allowing or denying specific IP ranges and protocols.

  10. What is the AWS Shared Responsibility Model?

    • Answer: The AWS Shared Responsibility Model defines the division of security responsibilities:
      • AWS's responsibility: Securing the infrastructure that runs all services, including hardware, software, networking, and facilities.
      • Customer's responsibility: Securing data, managing identity and access, configuring security settings, and compliance with regulations.

Advanced Level

  1. How do you design a fault-tolerant architecture on AWS?

    • Answer: To design a fault-tolerant architecture:
      • Use multiple Availability Zones (AZs) to spread out resources.
      • Implement load balancers to distribute traffic.
      • Use Auto Scaling to ensure redundancy.
      • Employ Multi-AZ deployments for databases like RDS.
      • Implement cross-region replication for disaster recovery.

  2. What is the difference between Amazon S3 and Amazon EFS?

    • Answer: S3 is an object storage service suitable for storing unstructured data like backups, media, and logs. EFS (Elastic File System) is a scalable file storage service for use with AWS services and on-premises resources. EFS is suitable for shared file storage for applications running on multiple EC2 instances.

  3. How do you optimize AWS costs?

    • Answer: AWS cost optimization can be achieved by:
      • Right-sizing instances based on utilization.
      • Using Reserved Instances for long-term workloads.
      • Leveraging Spot Instances for non-critical tasks.
      • Using S3 lifecycle policies to move infrequently accessed data to cheaper storage classes.
      • Monitoring and analyzing costs using AWS Cost Explorer and Budgets.

  4. What is Amazon Route 53, and how does it work?

    • Answer: Amazon Route 53 is a scalable DNS (Domain Name System) web service designed to route end users to internet applications by translating domain names into IP addresses. Route 53 also offers domain registration, health checks, and traffic routing policies (e.g., failover, latency-based).

  5. What are AWS CloudFormation and Terraform, and how do they differ?

    • Answer: AWS CloudFormation is an AWS service that enables infrastructure as code (IaC) within AWS, allowing you to define AWS resources in templates. Terraform is an open-source IaC tool by HashiCorp that supports multi-cloud environments, including AWS, Azure, GCP, and on-premises.

  6. How do you implement disaster recovery in AWS?

    • Answer: Disaster recovery in AWS can be implemented using various strategies:
      • Backup and Restore: Regularly back up data and restore it when needed.
      • Pilot Light: Maintain a minimal version of your environment running in the cloud.
      • Warm Standby: A scaled-down version of a fully functional environment is always running.
      • Multi-Site: Fully operational environments running simultaneously in different regions.

  7. What is Amazon Redshift, and what are its use cases?

    • Answer: Amazon Redshift is a fully managed data warehousing service designed for large-scale data analysis. It is used for running complex queries on structured and semi-structured data, making it ideal for business intelligence, reporting, and analytics.

  8. How does AWS Kinesis work for real-time data processing?

    • Answer: AWS Kinesis is a platform for real-time data streaming and processing. It consists of:
      • Kinesis Data Streams: Captures and processes large streams of data records in real-time.
      • Kinesis Data Firehose: Loads streaming data into data lakes and analytics services.
      • Kinesis Data Analytics: Processes and analyzes streaming data using SQL.

  9. What is AWS Direct Connect, and why would you use it?

    • Answer: AWS Direct Connect is a service that establishes a dedicated network connection between your data center and AWS. It offers a more consistent network experience than VPN, reduces bandwidth costs, and provides higher security.

  10. How would you secure an AWS environment?

    • Answer: Securing an AWS environment involves:
      • IAM best practices: Implementing least privilege, MFA, and role-based access.
      • VPC security: Using security groups, Network ACLs, and VPC Peering.
      • Data encryption: Encrypting data at rest and in transit using AWS KMS and SSL/TLS.
      • Monitoring and logging: Enabling CloudTrail, CloudWatch, and GuardDuty for continuous monitoring.
      • Compliance: Adhering to industry standards and frameworks relevant to your organization.

Scenario-Based Questions

  1. How would you migrate an on-premises application to AWS?

    • Answer:
      • Assess the application: Understand the architecture, dependencies, and data requirements.
      • Choose the right migration strategy: Rehosting, replatforming, or refactoring.
      • Set up the AWS environment: Create a VPC, configure subnets, and set up security groups.
      • Data migration: Use AWS Database Migration Service (DMS) or S3 Transfer Acceleration.
      • Deploy the application: Use EC2, RDS, and other necessary services.
      • Testing: Validate the deployment, ensuring functionality and performance.
      • Cutover: Transition traffic from the on-premises system to AWS.

  2. You need to set up a multi-tier web application on AWS. How would you design it?

    • Answer:
      • Front-end tier: Use an Elastic Load Balancer (ELB) to distribute traffic to EC2 instances running web servers.
      • Application tier: Deploy the application logic on another set of EC2 instances in private subnets.
      • Database tier: Use Amazon RDS in a Multi-AZ setup for high availability.
      • Security: Secure the environment using Security Groups, IAM roles, and SSL certificates.
      • Scaling: Set up Auto Scaling groups for both the web and application tiers.
      • Content delivery: Use CloudFront for caching static content.

  3. How would you handle a sudden increase in traffic to your AWS-hosted website?

    • Answer:
      • Auto Scaling: Ensure Auto Scaling is set up to automatically add EC2 instances based on CPU utilization.
      • Elastic Load Balancer: Use ELB to distribute traffic evenly across multiple instances.
      • CloudFront: Utilize CloudFront to cache static content and reduce the load on the origin servers.
      • Database optimization: Use read replicas or a caching layer like ElastiCache to offload read traffic from the primary database.

  4. A company wants to move to a serverless architecture. How would you implement this on AWS?

    • Answer:
      • APIs: Use API Gateway to expose APIs.
      • Compute: Implement AWS Lambda for executing business logic.
      • Data storage: Use DynamoDB for database needs, or S3 for file storage.
      • Messaging: Use SNS or SQS for inter-service communication.
      • Monitoring: Set up CloudWatch for logging, monitoring, and alerting.

  5. Your application needs to store and retrieve large amounts of unstructured data. Which AWS service would you use and why?

    • Answer: Amazon S3 would be the best choice for storing large amounts of unstructured data because it offers:
      • Scalability: Easily scales to store any amount of data.
      • Durability: 11 nines of durability ensures data is safe.
      • Cost-effectiveness: S3 offers various storage classes to optimize costs based on access frequency.
      • Integration: Seamlessly integrates with other AWS services for data processing and analysis.

Behavioral Questions

  1. Can you describe a challenging project you worked on using AWS and how you overcame obstacles?

    • Answer: (Example scenario) "In a recent project, I was tasked with migrating a legacy application to AWS. The challenge was maintaining zero downtime while ensuring data integrity. I implemented a pilot light strategy, setting up a minimal environment on AWS and syncing data in real-time. By running thorough tests and having a rollback plan in place, we successfully migrated the application with no disruption to users."

  2. How do you stay updated with the latest AWS features and best practices?

    • Answer:
      • "I regularly read AWS blogs, whitepapers, and documentation.
      • I attend AWS webinars and conferences, and I’m active in online communities like the AWS subreddit and Stack Overflow.
      • I also keep my skills current by working on projects and earning certifications."

  3. Describe a time when you optimized the cost of an AWS environment.

    • Answer:
      • "In a previous role, I noticed we were using On-Demand Instances for long-term workloads. I recommended and implemented Reserved Instances, which reduced our costs by 30%. Additionally, I identified underutilized resources and right-sized instances to further optimize our spending."

  4. How do you ensure security and compliance in an AWS environment?

    • Answer:
      • "I start by implementing IAM best practices, ensuring least privilege and MFA.
      • I use AWS Config to monitor compliance with policies and guardrails.
      • I also enable encryption for data at rest and in transit, and regularly audit security groups and network ACLs.
      • Finally, I use tools like AWS CloudTrail and GuardDuty for continuous monitoring and threat detection."

  5. Have you ever had to troubleshoot an AWS service issue? How did you resolve it?

    • Answer:
      • "Yes, I once encountered an issue where an EC2 instance wasn’t accessible. After checking the security groups and network ACLs, I realized the issue was due to a misconfigured route table in the VPC. I corrected the route to the internet gateway, and the instance became accessible immediately. This experience highlighted the importance of methodically diagnosing network-related issues."