1. What is AWS?
AWS (Amazon Web Services) is a cloud computing platform that provides on-demand services such as compute, storage, databases, networking, and AI on a pay-as-you-go basis.
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2. What are the core services provided by AWS?
Compute (EC2, Lambda, ECS)
Storage (S3, EBS, Glacier)
Database (RDS, DynamoDB, Aurora)
Networking (VPC, Route 53, ELB)
Security (IAM, KMS, Shield)
Monitoring (CloudWatch, CloudTrail)
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3. Explain the difference between IaaS, PaaS, and SaaS.
IaaS (Infrastructure as a Service): Provides virtualized computing resources (e.g., EC2, VPC).
PaaS (Platform as a Service): Provides managed platforms for application deployment (e.g., Elastic Beanstalk).
SaaS (Software as a Service): Provides ready-to-use software over the internet (e.g., Gmail, Salesforce).
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4. What is EC2?
Amazon EC2 (Elastic Compute Cloud) is a scalable virtual server service in AWS that allows you to run applications in the cloud.
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5. What is S3 and what are its main features?
Amazon S3 (Simple Storage Service) is an object storage service.
Features:
Unlimited storage
99.999999999% (11 9’s) durability
Versioning
Lifecycle policies
Different storage classes
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6. What is the purpose of an IAM role?
IAM Roles provide temporary permissions to entities like EC2, Lambda, or applications without embedding credentials.
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7. What is a VPC?
Amazon VPC (Virtual Private Cloud) is a logically isolated network where you can launch AWS resources securely.
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8. How do you secure a VPC?
Use Security Groups and Network ACLs
Enable VPC Flow Logs
Use private subnets for sensitive resources
Deploy VPN/Direct Connect for private connectivity
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9. What is the difference between public and private subnets?
Public subnet: Resources accessible from the internet (via Internet Gateway).
Private subnet: Resources not directly accessible from the internet (use NAT for outbound).
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10. Explain the concept of regions and availability zones.
Region: Geographical area (e.g., us-east-1).
Availability Zone (AZ): Physically separate datacenters within a region.
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11. What is a security group in AWS?
A virtual firewall that controls inbound and outbound traffic at the instance level.
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12. What is the purpose of Amazon RDS?
Amazon RDS (Relational Database Service) is a managed service for relational databases (MySQL, PostgreSQL, Oracle, SQL Server, Aurora).
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13. What is the difference between Amazon RDS and DynamoDB?
RDS: Relational, SQL-based, structured schema.
DynamoDB: NoSQL, key-value/document, highly scalable.
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14. How does AWS Lambda work?
AWS Lambda runs code in response to events (event-driven computing) without managing servers.
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15. What is CloudFront?
Amazon CloudFront is a CDN (Content Delivery Network) that caches and delivers content globally with low latency.
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16. What is the difference between EBS and EFS?
EBS (Elastic Block Store): Block storage, attached to a single EC2 instance.
EFS (Elastic File System): Shared file storage, scalable, accessible by multiple instances.
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17. What are the benefits of using AWS CloudFormation?
Infrastructure as Code
Automated deployments
Version control for infrastructure
Reusability via templates
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18. What is the AWS Free Tier?
A program that allows free usage of specific AWS services for 12 months (like 750 hrs EC2, 5GB S3, 750 hrs RDS).
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19. What is the role of the AWS Management Console?
A web-based GUI for managing AWS services.
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20. How do you monitor AWS services?
Using CloudWatch (metrics, alarms, dashboards) and CloudTrail (API logs).
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21. What is an AWS bucket policy?
A JSON-based policy attached to an S3 bucket to define permissions.
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22. What are tags in AWS?
Key-value pairs used for identifying and organizing resources (cost tracking, automation, management).
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23. What is Route 53?
A DNS web service that provides domain registration, routing, and health checks.
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24. How does Elastic Load Balancing work?
Distributes traffic across multiple targets (EC2, containers, Lambda) for scalability and fault tolerance.
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25. What is Auto Scaling?
Automatically adjusts the number of EC2 instances based on demand.
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26. What is the AWS Shared Responsibility Model?
AWS manages security of the cloud (infrastructure).
Customer manages security in the cloud (apps, data, IAM).
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27. What are AWS Regions and Availability Zones?
(Answered in Q10 – repeat with emphasis for interviewer)
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28. What is CloudWatch?
Monitoring and observability service for metrics, logs, and alarms.
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29. Explain what a key pair is in EC2.
A combination of public and private keys used for secure SSH/RDP access to EC2 instances.
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30. How do you upload files to S3?
AWS Console
AWS CLI (`aws s3 cp`)
SDKs (Python Boto3, etc.)
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31. What is AWS Glacier?
Now called S3 Glacier, used for low-cost archival storage.
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32. What is a bastion host?
A secure EC2 instance in a public subnet used to access resources in a private subnet.
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33. What is the difference between a VPN and AWS Direct Connect?
VPN: Secure internet-based connection.
Direct Connect: Dedicated private connection between on-premise and AWS.
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34. What is the purpose of AWS CodePipeline?
A CI/CD service for automating build, test, and deployment.
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35. What is Amazon SNS?
A notification service for pub/sub messaging.
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36. What are the different storage classes in S3?
Standard
Standard-IA (Infrequent Access)
One Zone-IA
Glacier
Glacier Deep Archive
Intelligent-Tiering
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37. Explain AWS Elastic Beanstalk.
A PaaS service for deploying and managing applications without managing infrastructure.
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38. What is AWS Inspector?
An automated security assessment service for EC2 and applications.
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39. How do you perform backups in AWS?
EBS snapshots
RDS automated backups
S3 versioning
AWS Backup service
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40. What are the pricing models for AWS services?
On-Demand
Reserved Instances
Spot Instances
Savings Plans
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1. How does AWS handle data replication?
AWS replicates data across Availability Zones to ensure durability and high availability.
Example:
S3 replicates objects automatically across multiple AZs.
RDS Multi-AZ creates a standby replica in another AZ.
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2. Explain the concept of Elasticity in AWS.
Elasticity means the ability to scale resources up or down automatically based on demand (e.g., Auto Scaling EC2 instances).
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3. What are the benefits of using AWS CloudFormation templates?
Automates infrastructure deployment
Version-controlled infrastructure as code
Consistent environments
Easy rollback on errors
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4. How can you ensure high availability in AWS?
Deploy across multiple AZs/Regions
Use ELB + Auto Scaling
Enable RDS Multi-AZ
Use Route 53 health checks
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5. Describe the AWS Well-Architected Framework.
It has 5 pillars:
1. Operational Excellence
2. Security
3. Reliability
4. Performance Efficiency
5. Cost Optimization
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6. What is the difference between AWS Lambda and EC2?
Lambda: Serverless, event-driven, short-running tasks.
EC2: Full control, runs long processes, manual scaling.
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7. What are the types of Elastic Load Balancers?
Application Load Balancer (ALB): Layer 7, HTTP/HTTPS traffic.
Network Load Balancer (NLB): Layer 4, TCP/UDP, high performance.
Classic Load Balancer (CLB): Older, basic Layer 4/7.
Gateway Load Balancer (GLB): Used for third-party appliances (firewalls).
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8. How does Amazon S3 versioning work?
When versioning is enabled, every object modification results in a new version, while older versions are preserved.
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9. Explain the role of Amazon CloudTrail.
CloudTrail records API calls made in AWS, used for auditing, compliance, and security analysis.
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10. What is AWS Kinesis and when would you use it?
AWS Kinesis is a real-time data streaming service, used for IoT, logs, analytics, and live monitoring
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11. How can you implement a multi-account architecture in AWS?
Use AWS Organizations for centralized management.
Apply Service Control Policies (SCPs).
Enable Consolidated Billing.
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12. What is the purpose of AWS Organizations?
Centralized account management, consolidated billing, and applying policies across accounts.
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13. Explain the difference between NAT Gateway and NAT Instance.
NAT Gateway: Managed, highly available, scales automatically.
NAT Instance: EC2-based, manual management, less scalable.
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14. What is AWS Direct Connect and when would you use it?
A dedicated private connection between on-premises and AWS. Used when low latency and consistent network performance is required.
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15. How do you perform cost management in AWS? Use AWS Cost Explorer & Budgets
Apply tags for cost allocation
Use Savings Plans / Reserved Instances
Monitor with Trusted Advisor
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16. What is AWS Systems Manager?
A management service for patching, configuration, and automating operational tasks across AWS resources.
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17. How do you secure data in transit in AWS?
Use SSL/TLS for encryption
Use AWS Certificate Manager (ACM)
Enable VPN/Direct Connect encryption
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18. Explain the concept of API Gateway.
Amazon API Gateway is a fully managed service for creating, publishing, and managing APIs at scale.
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19. What are the differences between Amazon RDS and Aurora?
RDS: Managed relational databases (MySQL, PostgreSQL, etc.).
Aurora: AWS-optimized, MySQL/PostgreSQL compatible, 5x faster than RDS MySQL.
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20. How do you configure cross-region replication in S3?
Enable Cross-Region Replication (CRR) with a destination bucket in another region and apply proper IAM roles.
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21. What is AWS Step Functions?
A service that coordinates serverless workflows by defining steps and sequencing functions.
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22. Explain how to implement a CI/CD pipeline in AWS.
CodeCommit (source control)
CodeBuild (build/test)
CodeDeploy (deployment)
CodePipeline (orchestration)
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23. What is Amazon Elastic Kubernetes Service (EKS)?
A managed Kubernetes service to run containerized applications on AWS without managing control planes.
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24. What is the difference between scheduled and event-driven Lambda functions?
Scheduled: Triggered by CloudWatch events (cron jobs).
Event-driven: Triggered by S3, DynamoDB, API Gateway events.
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25. How do you handle stateful applications in AWS?
Use EBS volumes, EFS, or RDS for persistence.
For containers, use EKS with persistent storage.
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26. Explain how AWS DMS works.
AWS Database Migration Service migrates databases with minimal downtime, supporting homogeneous (MySQL → MySQL) and heterogeneous (Oracle → PostgreSQL) migrations.
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27. What are the considerations for choosing an instance type in EC2?
Workload type (compute, memory, storage, GPU)
Performance requirements
Cost optimization
Networking needs
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28. How can you implement disaster recovery in AWS?
Backup & Restore
Pilot Light
Warm Standby
Multi-site Active-Active
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29. What is AWS Config?
A service to track and audit resource configurations and compliance over time.
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30. What is the purpose of AWS Secrets Manager?
To store, rotate, and manage secrets (passwords, API keys, database credentials).
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31. How does AWS Batch work?
AWS Batch runs batch processing workloads efficiently by managing job scheduling and computing resources automatically.
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32. What are CloudFormation nested stacks?
A stack within another CloudFormation stack, used to reuse templates and manage complex infrastructure.
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33. Explain the use of Amazon Elasticsearch Service (now OpenSearch Service).
A managed service for search, logging, and analytics (used with ELK stack).
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34. What are the different types of Amazon RDS instance classes?
Standard Classes (db.m5, db.m6g): Balanced compute and memory.
Memory-optimized (db.r5, db.r6g): High memory workloads.
Burstable (db.t3): Cost-effective, low workloads.
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35. How can you optimize costs in AWS?
Right-size instances
Use Reserved Instances or Savings Plans
Enable Auto Scaling
Use S3 lifecycle policies
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36. Describe the use cases for Amazon Redshift.
A data warehouse for big data analytics, BI, reporting, and data mining.
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37. What is AWS Global Accelerator?
A networking service that improves global application performance by routing traffic via AWS edge locations.
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38. How do you manage serverless applications in AWS?
Use AWS SAM (Serverless Application Model)
Monitor with CloudWatch
Deploy with CodePipeline
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39. Explain the role of Amazon SQS.
Amazon SQS (Simple Queue Service) is a fully managed message queuing service used for decoupling applications.
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40. What is the AWS Backup service?
A centralized service to automate backups across AWS services (EBS, RDS, DynamoDB, EFS, Storage Gateway).
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Experienced-Level AWS Interview Questions
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1. How would you design a multi-tier application architecture in AWS?
Presentation layer (Web): Deployed on ALB + EC2 or CloudFront.
Application layer: Auto Scaling group of EC2 or containers (ECS/EKS).
Database layer: RDS Multi-AZ or Aurora.
Security: VPC with public & private subnets, security groups, WAF.
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2. Explain the trade-offs between using AWS Lambda vs. containerized services.
Lambda: Event-driven, low-cost, no infrastructure management, but limited execution time (15 mins).
Containers (ECS/EKS): Long-running apps, greater control, higher cost, more operational effort.
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3. How do you implement security best practices in AWS?
Use IAM least privilege
Enable MFA
Encrypt data at rest & in transit
Enable CloudTrail, GuardDuty, Security Hub
Use WAF & Shield for DDoS protection
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4. What is AWS Transit Gateway, and when would you use it?
Transit Gateway connects multiple VPCs and on-premises networks through a central hub, simplifying large network topologies.
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5. Describe how to architect for resilience in AWS.
Deploy across multiple AZs/Regions
Use Auto Scaling + ELB
Store data in multi-AZ storage (S3, Aurora, DynamoDB)
Use disaster recovery strategies
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6. Explain the concept of microservices and how AWS supports them.
Microservices = loosely coupled, independently deployable services.
AWS support:
ECS/EKS for containers
API Gateway + Lambda
SQS/SNS/EventBridge for communication
CloudWatch & X-Ray for monitoring
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7. How do you ensure compliance in AWS?
Use AWS Artifact for compliance reports
Enable CloudTrail & Config
Apply IAM policies & SCPs
Use Audit Manager for regulatory frameworks (HIPAA, PCI-DSS, etc.)
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8. What are the key considerations for migrating to AWS?
Application dependency mapping
Data transfer strategies (Snowball, DMS, Direct Connect)
Security and compliance requirements
Cost optimization planning
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9. How do you handle large-scale data processing in AWS?
Kinesis or MSK for streaming
EMR (Hadoop/Spark) for batch processing
Glue for ETL
Redshift for analytics
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10. What is Amazon SageMaker, and how can it be used?
A fully managed ML service to build, train, and deploy machine learning models at scale.
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11. Explain how AWS App Mesh works.
App Mesh provides service mesh functionality:
Controls service-to-service communication
Enables observability (metrics, logs, tracing)
Improves reliability with retries, failover
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12. Describe the use of AWS Glue.
A serverless ETL service that discovers, prepares, and transforms data for analytics and machine learning.
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13. How can you implement service discovery in AWS?
Use Route 53 Private Hosted Zones
Cloud Map for naming services
ECS/EKS internal service discovery
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14. What strategies can you use for database migration to AWS?
Lift & Shift (using DMS)
Re-platforming (e.g., Oracle → Aurora)
Re-architecting (monolith → microservices + DynamoDB)
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15. Explain how to optimize Amazon RDS performance.
Enable read replicas
Use Aurora for high performance
Optimize indexes & queries
Use Provisioned IOPS storage
Enable caching (ElastiCache)
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16. What is Amazon FSx, and when would you use it?
A fully managed file system:
FSx for Windows: Windows workloads.
FSx for Lustre: High-performance computing.
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17. Describe the importance of logging and monitoring in AWS.
Ensures security, compliance, and troubleshooting.
Tools: CloudWatch (metrics/logs), CloudTrail (API logs), X-Ray (tracing), GuardDuty (threat detection).
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18. How do you implement a secure API with AWS API Gateway?
Use IAM, Cognito, or Lambda authorizers for authentication
Enable WAF & throttling
Enable SSL/TLS encryption
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19. What are the considerations for using serverless architectures?
Cold starts impact latency
Timeout limits (15 mins in Lambda)
State management (must use DynamoDB, S3, etc.)
Cost efficiency for burst workloads
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20. How do you troubleshoot performance issues in AWS?
Use CloudWatch & X-Ray for metrics and tracing
Check Auto Scaling configurations
Monitor network bottlenecks (VPC Flow Logs)
Optimize DB queries
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21. What is AWS Data Pipeline, and how is it used?
A data workflow orchestration service to move and transform data between S3, RDS, EMR, Redshift.
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22. Describe the best practices for deploying applications using AWS CloudFormation.
Use nested stacks for modular design
Enable rollback on failure
Use parameterized templates
Store in version control (Git)
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23. How do you manage secrets in a serverless architecture?
Use AWS Secrets Manager
Use SSM Parameter Store
Never hardcode secrets in Lambda code
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24. What is the role of AWS WAF?
AWS Web Application Firewall protects applications from SQL injection, XSS, DDoS attacks.
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25. Explain how you would architect a global application in AWS.
Deploy in multiple regions
Use Route 53 latency-based routing
Use CloudFront CDN
Store data in Aurora Global Database / DynamoDB Global Tables
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26. What are the key performance indicators for AWS services?
EC2: CPU, memory, network usage
RDS: Latency, IOPS, connections
S3: Request rate, errors
Lambda: Invocation count, duration, errors
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27. How do you conduct a cost analysis for AWS services?
Use AWS Cost Explorer
Enable detailed billing reports
Apply resource tags
Analyze RI/Savings Plan utilization
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28. Describe a scenario where you would use AWS Step Functions.
For orchestrating workflows: e.g., image processing pipeline where Lambda → Rekognition → S3 → DynamoDB in sequence.
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29. What is Amazon Kinesis Data Firehose?
A service to capture, transform, and load real-time data streams into S3, Redshift, or Elasticsearch.
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30. How do you implement Continuous Deployment in AWS?
Use CodeCommit + CodeBuild + CodeDeploy + CodePipeline
Integrate with CloudFormation / Elastic Beanstalk
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31. What is AWS Service Catalog?
A service that allows organizations to create and manage approved resource templates for self-service deployment.
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32. Describe how to handle event-driven architecture in AWS.
Use SNS/SQS/EventBridge for event communication
Trigger Lambda functions for processing
Ensure idempotency and retry policies
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33. Explain how to secure a serverless application.
Use IAM least privilege for Lambda
Store secrets in Secrets Manager
Apply API Gateway authentication + WAF
Enable logging with CloudWatch
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34. What are AWS PrivateLink and its use cases?
AWS PrivateLink allows private connectivity to services across VPCs without exposing data to the internet.
Use cases: secure SaaS integration, VPC-to-VPC connectivity.
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35. How do you optimize Lambda function performance?
Increase memory allocation (also increases CPU)
Use provisioned concurrency
Minimize package size
Reuse execution context
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36. What is AWS Control Tower?
A service to set up and govern multi-account AWS environments following AWS best practices.
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37. Explain the use of Amazon QuickSight.
A business intelligence (BI) service for creating dashboards and data visualizations from AWS and external data sources.
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38. How do you manage hybrid cloud environments with AWS?
Use Direct Connect or VPN for connectivity
Deploy Outposts for on-prem workloads
Use Storage Gateway for hybrid storage
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39. What is Amazon Neptune?
A fully managed graph database service supporting Gremlin and SPARQL queries (used for social networks, fraud detection).
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40. How do you evaluate and improve the architecture of an AWS solution?
Use the AWS Well-Architected Tool
Run Trusted Advisor checks
Analyze CloudWatch/Cost Explorer metrics
Apply security audits with Inspector & Config
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