Amazon Web Services (AWS) Interview Questions and Answers 2025

Amazon Web Services (AWS) is a comprehensive cloud computing platform provided by Amazon. It offers a wide range of services including computing power, storage, databases, networking, analytics, machine learning, and security, allowing businesses to scale and innovate quickly.

EC2 (Elastic Compute Cloud) provides resizable compute capacity in the cloud, allowing you to run virtual servers. S3 (Simple Storage Service) is an object storage service used to store and retrieve any amount of data at any time from anywhere on the web.

AWS Identity and Access Management (IAM) enables you to manage access to AWS services and resources securely. It allows you to create and manage users, groups, and permissions, ensuring that only authorized users can access specific resources.

AWS Lambda is a serverless compute service that lets you run code without provisioning or managing servers. You only pay for the compute time you consume, and Lambda automatically scales your application by running code in response to events.

An Amazon Virtual Private Cloud (VPC) allows you to provision a logically isolated section of the AWS cloud where you can launch AWS resources in a virtual network that you define. It provides control over network configuration, security, and routing.

AWS divides its global infrastructure into regions, which are separate geographic areas. Each region contains multiple, isolated locations known as Availability Zones. This design helps achieve high availability, fault tolerance, and disaster recovery.

AWS CloudFormation is a service that helps you model and set up your AWS resources using templates. It automates the provisioning and management of resources, making it easier to replicate environments and manage infrastructure as code.

AWS Auto Scaling automatically adjusts the number of compute resources based on demand. It helps maintain application performance and optimize costs by scaling resources up or down as needed.

A public subnet is a subnet whose instances can communicate directly with the internet using an internet gateway. A private subnet does not have direct access to the internet, and its instances typically communicate through a NAT gateway or other means.

AWS Elastic Beanstalk is a Platform as a Service (PaaS) that allows you to deploy and manage applications quickly without worrying about the underlying infrastructure. It automatically handles capacity provisioning, load balancing, scaling, and application health monitoring.

AWS RDS (Relational Database Service) is a managed service for relational databases like MySQL, PostgreSQL, and SQL Server. DynamoDB is a fully managed NoSQL database service designed for fast and predictable performance with seamless scalability.

AWS Route 53 is a scalable Domain Name System (DNS) web service that routes end-user requests to endpoints in a globally distributed, highly available manner. It supports health checks, routing policies, and integrates with other AWS services for failover and latency-based routing.

Security Groups act as virtual firewalls for EC2 instances, controlling inbound and outbound traffic at the instance level. Network ACLs (Access Control Lists) operate at the subnet level and provide stateless filtering of traffic entering or leaving a VPC.

AWS KMS is a managed service that enables you to create and control cryptographic keys used to encrypt your data. It integrates with many AWS services to provide centralized key management and audit capabilities.

A multi-AZ deployment in AWS RDS involves creating a primary database instance and synchronously replicating it to a standby instance in a different Availability Zone. This setup enhances availability and automatic failover in case of infrastructure failure.

AWS CloudTrail records API calls made on your account, providing a history of AWS service events. It helps with security analysis, resource change tracking, and compliance auditing by delivering log files to an S3 bucket.

S3 versioning allows you to keep multiple variants of an object in the same bucket. It helps protect against accidental deletions and overwrites, enabling you to restore previous versions of objects when needed.

AWS ELB automatically distributes incoming application traffic across multiple targets, such as EC2 instances. There are three types: Application Load Balancer (ALB), Network Load Balancer (NLB), and Classic Load Balancer (CLB), each suited for different use cases.

AWS Organizations allows you to centrally manage and govern multiple AWS accounts. It helps with consolidated billing, policy-based management, and automation of account creation, making it easier to manage resources at scale.

AWS Direct Connect establishes a dedicated network connection from your premises to AWS, providing lower latency and higher bandwidth compared to VPN, which uses encrypted connections over the public internet.

AWS CloudFront is a Content Delivery Network (CDN) that caches copies of your content at edge locations worldwide. It reduces latency and improves performance by delivering content closer to users.

AWS SNS (Simple Notification Service) is used for pub/sub messaging, while SQS (Simple Queue Service) is used for message queuing. Together, they enable decoupled, scalable, and fault-tolerant application architectures by allowing asynchronous communication between components.

Lifecycle policies in AWS (such as those in S3 or EBS) automate the transition and expiration of objects or snapshots. They help manage storage costs by moving data to cheaper storage classes or deleting it when no longer needed.

CloudWatch Logs Insights is an interactive log analytics service that helps you search and analyze log data in real time. It enables you to troubleshoot operational problems by querying logs and visualizing results.

AWS Control Tower automates the setup and governance of secure, multi-account AWS environments based on AWS best practices. It provides pre-configured blueprints, guardrails, and centralized management, making it easier to manage compliance, security, and account provisioning at scale.

Designing a highly available, fault-tolerant architecture involves using multiple AWS regions and Availability Zones, deploying resources redundantly, leveraging services like Elastic Load Balancer, Route 53 for DNS failover, S3 cross-region replication, and RDS Multi-AZ or Aurora Global Databases. Monitoring and automated recovery mechanisms are also essential.

ECS (Elastic Container Service) is AWS's native container orchestration service, EKS (Elastic Kubernetes Service) provides managed Kubernetes, and Fargate is a serverless compute engine for containers that works with both ECS and EKS, allowing you to run containers without managing servers.

A secure, scalable API can be implemented using Amazon API Gateway for endpoint management, AWS Lambda or ECS/EKS for compute, Cognito for authentication, WAF for protection, and CloudFront for caching. Use IAM roles and resource policies for fine-grained access control, and enable logging and monitoring with CloudWatch.

Migration involves assessing compatibility, choosing between homogeneous (e.g., MySQL to Aurora MySQL) or heterogeneous migration, using AWS Database Migration Service (DMS) for minimal downtime, planning for schema conversion, testing performance, and ensuring security and compliance throughout the process.

AWS supports zero-trust by enforcing least privilege access with IAM, using VPC security controls, enabling encryption in transit and at rest, leveraging AWS PrivateLink for private connectivity, and monitoring with services like GuardDuty and CloudTrail. Continuous authentication and authorization are key components.

Cost optimization involves using Auto Scaling, Spot Instances, Savings Plans, and Reserved Instances, choosing the right storage classes (e.g., S3 Intelligent-Tiering), leveraging serverless where possible, monitoring usage with Cost Explorer, and setting up budgets and alerts to track and control spending.

AWS Step Functions allows you to coordinate multiple AWS services into serverless workflows using state machines. It supports error handling, retries, parallel execution, and integrates with Lambda, ECS, and more, making it ideal for building resilient, auditable, and scalable business processes.

Strategies include enabling bucket encryption (SSE-S3, SSE-KMS), enforcing bucket policies and IAM permissions, enabling S3 Block Public Access, using Access Analyzer, enabling logging and monitoring with CloudTrail and CloudWatch, and implementing MFA Delete for critical buckets.

Compliance is achieved by using AWS services with relevant certifications, enabling security features (encryption, logging, monitoring), using AWS Artifact for documentation, implementing strong IAM policies, and leveraging AWS Config and Audit Manager for continuous compliance monitoring and reporting.

AWS Global Accelerator provides static IP addresses that route user traffic to optimal endpoints across AWS regions using the AWS global network. It improves performance by reducing latency and increases availability by automatically rerouting traffic in case of failures.

A serverless analytics pipeline can use Kinesis Data Streams or Firehose for ingestion, Lambda for processing, S3 for storage, Glue for ETL, Athena for querying, and QuickSight for visualization. Each component scales automatically and is managed by AWS, reducing operational overhead.

AWS Service Catalog allows organizations to centrally manage approved IT services, including VMs, databases, and applications. It enforces compliance by controlling which products are available, managing versions, and applying governance through tagging and permissions.

Best practices include using AWS Secrets Manager or Parameter Store to store and rotate secrets, restricting access with IAM policies, enabling audit logging, encrypting secrets at rest and in transit, and never hardcoding credentials in application code or repositories.

Use AWS X-Ray for distributed tracing, CloudWatch for metrics and logs, CloudWatch Alarms for alerting, and integrate with third-party tools if needed. Implement structured logging, correlation IDs, and centralized log aggregation to trace requests across services.

AWS Outposts extends AWS infrastructure, services, APIs, and tools to on-premises locations for workloads requiring low latency, local data processing, or data residency. It's ideal for hybrid cloud scenarios where applications need to run seamlessly across on-premises and AWS environments.