aws interview questions

AWS Interview Questions and Answers

August 24th, 2026
21912
30:00 Minutes

It may not be easy to clear AWS interviews as they are going to check your technical information and your success in the industry. I have experience working with AWS concepts and cloud technologies so I have been in the position of being an interviewee as well as an interviewer. 

The result of that experience is that I have prepared this blog with the most important questions and answers related to AWS interviews ranging from beginner to advanced level for preparations of those who want to succeed in AWS interviews.

Let’s start!

Read Also: Best Cloud Computing Services You Need to Know

AWS Interview Questions for Freshers

Let's start with fundamental AWS concepts that form the foundation of your interview preparation.

1. What is AWS?

AWS is a comprehensive cloud computing platform offered by Amazon. It provides on-demand computing services including servers, storage, databases, networking, analytics, machine learning, and security tools.

AWS operates on a pay-as-you-go pricing model. You only pay for the services you use without upfront investments. This flexibility makes AWS suitable for businesses of all sizes. The platform serves organizations ranging from startups to large enterprises.

2. What are the main benefits of AWS?

AWS offers numerous advantages that make it the preferred cloud provider:

BenefitDescription
ScalabilityEasily scale resources up or down based on demand without managing infrastructure
Cost-EffectivePay only for what you use with no upfront costs or long-term commitments
High AvailabilityMultiple availability zones ensure your applications remain online
Global InfrastructureAccess to data centers across multiple regions worldwide
SecurityComprehensive security tools, encryption, and compliance features
FlexibilityChoose from 200+ services to build your ideal solution
PerformanceLow-latency delivery with edge locations for fast content distribution
Reliability99.99% uptime SLA for most services

3. What are the types of cloud computing models?

AWS supports three main cloud computing models:

1. Infrastructure as a Service (IaaS): You manage applications, data, runtime, middleware, and OS. AWS manages virtualization, servers, storage, and networking. EC2 is a prime example.

2. Platform as a Service (PaaS): You manage applications and data only. AWS handles everything else including runtime, middleware, OS, and infrastructure. Elastic Beanstalk is a good example.

3. Software as a Service (SaaS): AWS manages everything. You simply use the application through a web browser. Salesforce is an example though not from AWS.

4. What is an AWS Region?

An AWS Region is a geographical area containing multiple Availability Zones. Each region is completely isolated from others, ensuring data residency and compliance requirements. AWS currently operates in multiple regions globally.

When you launch resources in AWS, you specify a region. All data and services in that region stay within that geographic location. This helps with latency, compliance, and disaster recovery planning.

5. What is an Availability Zone?

An Availability Zone (AZ) is one or more data centers within a region. Each AZ is isolated from others but connected through low-latency networks. This isolation helps achieve high availability and fault tolerance.

If one AZ experiences an outage, your resources in other AZs within the same region continue running. Most AWS regions contain at least three availability zones for redundancy.

Read Also: Top 10 AWS Alternatives For 2026

6. What is an Edge Location?

Edge Locations are AWS data centers located globally, separate from regions and availability zones. They are primarily used by CloudFront and Route 53 to deliver content with minimal latency.

Edge locations cache content closer to end users. This reduces latency and improves application performance. AWS has significantly more edge locations than regions, providing worldwide coverage.

7. What is AWS IAM?

IAM stands for Identity and Access Management. It is a service that controls who can access your AWS resources and what actions they can perform.

IAM allows you to create users, groups, and roles with specific permissions. You can grant fine-grained access control based on the principle of least privilege. This means users get only the permissions they need to perform their job.

8. What is the difference between an IAM User and an IAM Role?

AspectIAM UserIAM Role
Identity TypeLong-term credentials for a person or applicationTemporary credentials for AWS services or external entities
Access KeysPermanent access keys unless rotated manuallyTemporary security credentials that rotate automatically
Use CaseIndividual developers or applications needing persistent accessAWS services assuming permissions or cross-account access
CredentialsAccess Key ID and Secret Access KeyTemporary security token, access key, and secret key
PasswordCan have console passwordCannot have console password
DurationIndefinite until deletedSession has an expiration time
ExampleDeveloper accessing S3 bucketsEC2 instance accessing DynamoDB

9. What is an IAM Policy?

An IAM policy is a document that defines permissions. It specifies which AWS resources users can access and what actions they can perform.

Policies are written in JSON format. They follow the principle of least privilege by default denying all access unless explicitly granted. You attach policies to users, groups, or roles.

10. What is MFA in AWS?

MFA stands for Multi-Factor Authentication. It adds an extra layer of security by requiring two or more authentication methods.

MFA works by combining something you know (password) with something you have (authenticator device or app). Even if someone obtains your password, they cannot access your account without the second factor. This significantly improves account security.

AWS Interview Questions for Freshers

Once you master the basics, it is time to become job-ready. Here are key AWS interview questions for fresher-level positions.

1. What is EC2 and how does it differ from on-premises servers?

Amazon EC2 is Elastic Compute Cloud. It provides resizable computing capacity in the cloud. You can launch virtual machines called instances and manage them through the AWS Management Console.

EC2 differs from on-premises servers in several ways:

  • No upfront investment: You pay only for running instances

  • Instant provisioning: Launch new servers in minutes instead of weeks

  • Scalability: Add or remove capacity as needed

  • Managed infrastructure: AWS handles hardware maintenance

  • Global availability: Deploy across multiple regions

  • Multiple instance types: Choose from various configurations for different workloads

    Also Read: AWS vs Google Cloud Platform vs Azure: Key Comparisons

2. What are EC2 instance types?

EC2 instance types are grouped by purpose and optimized for different use cases:

1. General Purpose (T3, M5, M6): Balanced compute, memory, and networking. Use for web applications and small databases.

2. Compute Optimized (C5, C6): High-performance processing. Use for batch processing and scientific modeling.

3. Memory Optimized (R5, R6): Large in-memory databases and caches. Use for real-time analytics and in-memory databases.

4. Storage Optimized (I3, D2): High sequential I/O access. Use for NoSQL databases and data warehousing.

5. Accelerated Computing (P3, G4): GPU and FPGA instances. Use for machine learning and graphics processing.

3. What is an AMI?

AMI stands for Amazon Machine Image. It is a template containing the operating system, applications, and configurations needed to launch an EC2 instance.

You can create custom AMIs from existing instances. This allows you to launch multiple instances with identical configurations quickly. AMIs significantly reduce deployment time and ensure consistency across instances.

4. What is Auto Scaling in AWS?

Auto Scaling automatically adjusts the number of EC2 instances based on demand. You define minimum, maximum, and desired capacity along with scaling policies.

Auto Scaling works by monitoring metrics like CPU utilization or network traffic. When demand increases, it launches new instances. When demand decreases, it terminates unnecessary instances. This ensures optimal performance while minimizing costs.

5. What is an Elastic Load Balancer (ELB)?

An ELB distributes incoming application traffic across multiple targets. It prevents any single instance from becoming a bottleneck. ELB also performs health checks and routes traffic only to healthy instances.

ELB improves application availability and fault tolerance. If one instance fails, traffic automatically routes to healthy instances. This provides a seamless user experience during server failures.

6. What are the different types of Load Balancers in AWS?

AWS offers three types of load balancers:

1. Application Load Balancer (ALB): Best for HTTP and HTTPS traffic. It supports path-based and host-based routing. Use for web applications and microservices.

2. Network Load Balancer (NLB): Handles extreme performance and ultra-high throughput. Use for real-time applications and gaming platforms.

3. Classic Load Balancer (CLB): Legacy option for EC2-Classic environments. AWS recommends ALB or NLB for new applications.

7. What is Amazon S3?

Amazon S3 is Simple Storage Service. It is object-based storage that stores data as objects within containers called buckets.

S3 provides unlimited scalability and stores data across multiple devices and facilities. You access objects through HTTP. S3 is highly durable, with 99.999999999% durability designed for 11 nines of durability.

8. What is S3 versioning?

S3 versioning enables you to keep multiple versions of the same object. When enabled, S3 preserves all versions when you update or delete objects.

Versioning helps with accidental deletion recovery and data protection. You can restore previous versions if needed. This is useful for compliance and data retention requirements.

9. What is RDS?

RDS stands for Relational Database Service. It is a managed database service supporting engines like MySQL, PostgreSQL, Oracle, and SQL Server.

RDS handles database administration tasks including backups, patching, and replication. You focus on your application while AWS manages the infrastructure. Multi-AZ deployment ensures high availability.

10. What is DynamoDB?

DynamoDB is a fully managed NoSQL database service. It provides fast and predictable performance with seamless scalability.

DynamoDB is useful for applications requiring flexible schemas and horizontal scaling. It supports both document and key-value data models. DynamoDB is ideal for mobile apps, IoT devices, and real-time analytics.

AWS Interview Questions for Intermediates

These questions test deeper knowledge and practical experience with AWS services.

1. How does Auto Scaling work in AWS?

Auto Scaling uses scaling policies to automatically adjust capacity. Scaling policies define when and how many instances to add or remove.

1. Target Tracking Scaling: Maintains a specific metric like 70% CPU utilization. The Auto Scaling group automatically adjusts instance count to maintain the target.

2. Step Scaling: Increases or decreases capacity in steps based on CloudWatch alarm thresholds. Different steps can have different scaling adjustments.

Simple Scaling: Takes one action when a CloudWatch alarm triggers. Waits for cooldown period before responding to another alarm.

2. How does ELB distribute traffic across instances?

ELB uses algorithms to distribute traffic:

1. Round Robin: Distributes requests equally across all instances in sequence.

2. Least Outstanding Requests: Routes traffic to the instance with the fewest active requests.

3. Source IP Hash: Routes requests from the same client to the same instance.

Health checks ensure traffic only goes to healthy instances. ELB performs periodic health checks and removes unhealthy instances from the load balancing pool.

Related Article: MongoDB vs MySQL: Understanding Key Differences

3. What is an S3 Lifecycle Policy?

S3 Lifecycle Policies automatically manage object lifecycles. They define rules for transitioning objects between storage classes or deleting them.

You can set policies to move objects to Glacier after 90 days or delete them after one year. This reduces storage costs by moving infrequently accessed data to cheaper storage classes. Lifecycle policies are crucial for cost optimization.

4. What is S3 Replication?

S3 Replication automatically copies objects from one bucket to another. It enables disaster recovery and data redundancy across regions.

1. Same-Region Replication (SRR): Copies objects within the same region for compliance and testing.

2. Cross-Region Replication (CRR): Copies objects to different regions for disaster recovery and lower latency access.

Replication happens asynchronously. You can replicate only new objects or existing objects using the Replication Status tool.

5. What is a Pre-Signed URL in S3?

A pre-signed URL provides temporary access to S3 objects without requiring AWS credentials. The URL includes authentication embedded within it.

Pre-signed URLs are useful for sharing files securely without making objects public. You can set expiration times, limiting how long the URL remains valid. This allows temporary access without bucket policy changes.

6. What is S3 Event Notification?

S3 Event Notifications trigger actions when specific events occur on objects. Events include object creation, deletion, or restoration.

Notifications can trigger Lambda functions, SNS topics, or SQS queues. This enables automation like resizing images when uploaded or processing data files. Event notifications are essential for building serverless workflows.

7. What is Object Lifecycle Management in S3?

Object Lifecycle Management automates object transition and expiration. You create rules specifying when objects should transition to different storage classes or be deleted.

1. Transition Rules: Move objects to Glacier or Deep Archive after a set period.

2. Expiration Rules: Automatically delete objects after a specified date.

3. Noncurrent Version Rules: Delete old versions of versioned objects.

Lifecycle management reduces storage costs significantly by automatically managing object aging.

8. What is a NAT Gateway?

A NAT Gateway allows resources in private subnets to access the internet while remaining unreachable from the internet. NAT stands for Network Address Translation.

The NAT Gateway translates private IP addresses to public IP addresses. This provides outbound internet access without exposing private resources. NAT Gateways are highly available and support high throughput.

Read Also: How To Become An AWS Certified Developer Associate - A Guide To Follow

9. What is VPC Peering?

VPC Peering creates a network connection between two VPCs. It enables private communication between instances in different VPCs as if they were on the same network.

VPC Peering is useful for connecting applications across different VPCs or AWS accounts. Traffic remains private and does not traverse the internet. You can peer VPCs in the same region or different regions.

10. What is AWS VPN?

AWS VPN provides secure encrypted connections. It creates a tunnel between your on-premises network and AWS VPC.

1. Site-to-Site VPN: Connects entire networks. Useful for hybrid cloud setups.

2. Client VPN: Connects individual users to AWS resources. Ideal for remote workers.

VPN connections are encrypted and provide authentication. Traffic does not travel over the public internet, ensuring security.

AWS Interview Questions for Experienced Professionals

These advanced questions test architectural thinking and real-world experience.

1. How would you design a highly available architecture in AWS?

Designing high availability requires multiple strategies:

1. Use Multiple Availability Zones: Distribute resources across at least two availability zones. This protects against single data center failures.

2. Implement Load Balancing: Use Application Load Balancer or Network Load Balancer to distribute traffic. This prevents single instance failures from affecting availability.

3. Enable Auto Scaling: Configure Auto Scaling groups to maintain desired capacity. This handles traffic spikes automatically.

4. Use RDS Multi-AZ: Enable Multi-AZ deployment for RDS databases. This provides automatic failover to a standby instance.

5. Implement caching: Use ElastiCache or CloudFront to reduce database load and improve response times.

6. Monitor and Alert: Set up CloudWatch monitoring and SNS alerts for critical metrics. This enables rapid response to issues.

2. What is High Availability and how can it be achieved in AWS?

High Availability means your applications remain online and accessible even during component failures. It focuses on minimizing downtime.

You achieve high availability through:

  • Redundancy across multiple availability zones

  • Load balancing across instances

  • Auto Scaling to handle demand

  • Managed services with built-in redundancy

  • Regular backup and disaster recovery testing

  • Database replication and failover

3. What is Fault Tolerance and how does it differ from High Availability?

Fault Tolerance means your system continues operating even when components fail. The application experiences no downtime during failures.

High Availability focuses on minimizing downtime. Fault Tolerance focuses on zero downtime. Fault tolerance is a higher bar than high availability. It requires sophisticated redundancy and failover mechanisms.

For example, a website with load balancing is highly available. A system with automatic database failover and zero data loss is fault tolerant.

Read Also: How to Learn AWS From Scratch?

4. What is Horizontal Scaling and when would you use it?

Horizontal Scaling adds more instances to handle increased load. You distribute traffic across multiple instances.

Use horizontal scaling when:

  • You need to handle increased traffic

  • Your application is stateless or can share state in a cache

  • You want to avoid single-instance bottlenecks

  • You need cost-effective scaling

Horizontal scaling is easier to implement with Auto Scaling and load balancers.

5. What is Vertical Scaling and what are its limitations?

Vertical Scaling upgrades existing instances to larger sizes. You increase CPU, memory, or storage on a single instance.

Limitations of vertical scaling:

  • Requires instance downtime for upgrade

  • Creates single point of failure

  • Limited by maximum instance size

  • Does not improve fault tolerance

  • Can be more expensive than horizontal scaling

Use vertical scaling when your application requires powerful single instances.

6. How does Load Balancing improve application performance and availability?

Load Balancing distributes traffic across multiple instances. This improves performance and availability:

1. Performance: Traffic distribution prevents any single instance from becoming a 1. bottleneck. This ensures consistent response times.

2. Availability: If one instance fails, load balancer routes traffic to remaining healthy instances. Users experience no downtime.

3. Scalability: Load balancers work with Auto Scaling to handle traffic spikes. Additional instances automatically start when needed.

4. Health Checks: Load balancers perform health checks and remove unhealthy instances. This ensures traffic only goes to working servers.

7. What is Block Storage and when should it be used?

Block Storage provides storage volumes that attach to instances. Amazon EBS is AWS block storage service.

Use Block Storage when:

  • You need consistent low-latency access

  • You require random I/O operations

  • You want to attach storage to EC2 instances

  • You need persistent storage that survives instance termination

  • You are running traditional databases

Block storage offers high performance but requires instance attachment.

Read Also: AWS Certified DevOps Engineer: An Exam Preparation Guide

8. What is File Storage and when is it preferred?

File Storage allows multiple instances to access files simultaneously. Amazon EFS is AWS file storage service.

Use File Storage when:

  • Multiple instances need shared file access

  • You are running applications requiring shared file systems

  • You need automatic scaling and high availability

  • You want to avoid managing NAS infrastructure

File storage is ideal for content management and media processing.

9. What is Object Storage and how does it differ from block and file storage?

Object Storage stores files as complete objects with metadata. Amazon S3 is AWS object storage.

Key differences:

AspectBlock StorageFile StorageObject Storage
AccessAttached to instancesNetwork sharedHTTP/API
PerformanceLow latencyMedium latencyHigh latency but unlimited scale
Use CaseDatabases, OSShared filesBackup, archive, data lakes
ScalabilityLimited by instanceLimited by file systemUnlimited
CostHigher per GBMediumLowest

10. What is the difference between Spot, Reserved and On-Demand Instances?

Instance TypeCostCommitmentInterruptionUse Case
On-DemandHighestNoneNoneProduction workloads, unpredictable traffic
Reserved30-40% cheaper1 or 3 yearsNoneStable, long-term workloads
Spot70-90% cheaperNoneCan terminateBatch jobs, fault-tolerant apps

Use a combination for cost optimization. Use Reserved for baseline capacity and Spot for additional capacity.

AWS AI and Generative AI Interview Questions

AI and Generative AI are the fastest-growing areas in AWS. Prepare for these emerging questions.

1. What is Amazon Bedrock and how does it differ from Amazon SageMaker?

Amazon Bedrock is a managed service that provides access to foundation models from multiple providers. You can invoke foundation models through a simple API without managing infrastructure.

Amazon SageMaker is for building, training, and deploying machine learning models. It provides more control and flexibility for custom machine learning workflows.

Key Differences:

  • Bedrock: Pre-trained foundation models, easier to use, lower barrier to entry

  • SageMaker: Build custom models, more control, steeper learning curve

  • Bedrock: Less customization options

  • SageMaker: Extensive customization and fine-tuning capabilities

Use Bedrock for quick generative AI implementation. Use SageMaker for custom machine learning solutions.

2. How do you choose the right Foundation Model for a Generative AI application?

Consider these factors:

1. Task Type: Text generation, image generation, or multimodal tasks.

2. Model Capabilities: Different models excel at different tasks. Some are better for coding, others for creative writing.

3. Latency Requirements: Smaller models respond faster. Larger models provide better quality but slower response.

4. Cost: Token pricing varies by model. Track your usage patterns to estimate costs.

5. Accuracy Needs: Test models on your specific use cases. Benchmark against your requirements.

6. Compliance: Some models have specific data handling or training policies.

Start with popular models like Claude, then experiment with others based on your results.

3. What is Retrieval-Augmented Generation (RAG) and why is it preferred over fine-tuning in some use cases?

RAG retrieves relevant documents from a knowledge base and passes them to a foundation model. The model generates responses based on retrieved context.

RAG Advantages:

  • Works with current information without retraining

  • Reduces hallucinations by grounding in factual data

  • Updates knowledge without model retraining

  • Lower cost than fine-tuning

  • Faster to implement

Fine-tuning Advantages:

  • Adapts model behavior to specific style

  • Better for domain-specific language patterns

  • Improves consistency across generations

Use RAG for fact-heavy applications. Use fine-tuning for style and behavior adaptation.

Also Read: What are The Differences Between SaaS, PaaS and IaaS?

4. How would you build a RAG application using Amazon Bedrock and Amazon S3?

Architecture:

  1. Store documents in S3: Upload your knowledge base documents to S3 buckets.

  2. Create Bedrock Knowledge Base: Use Bedrock Knowledge Bases to index documents and create embeddings.

  3. Set up retrieval: Configure retrieval settings for your documents.

  4. Build application: Use Bedrock Converse API to query the knowledge base and generate responses.

  5. Implement guardrails: Add output filtering to prevent harmful responses.

5. What is Amazon Bedrock Guardrails and how does it help secure AI applications?

Bedrock Guardrails filter harmful content from foundation model outputs. You define policies controlling what the model can generate.

Capabilities:

  • Content filtering: Block inappropriate content categories

  • Sensitive information filtering: Prevent exposure of PII and secrets

  • Custom policies: Define organization-specific rules

  • Audit logging: Track all generations for compliance

Guardrails are essential for production applications. They ensure AI outputs align with your policies.

6. How can you prevent hallucinations in Generative AI applications on AWS?

Hallucinations are false information generated by models. Prevent them through:

1. Use RAG: Ground responses in factual data from your knowledge base. This reduces hallucinations significantly.

2. Prompt Engineering: Write clear, specific prompts that guide the model toward factual responses.

3. Temperature and Top-P: Lower these values to make outputs more deterministic and focused.

4. Fact Checking: Implement post-processing to verify facts against your knowledge base.

5. Model Selection: Some models hallucinate less than others. Test with your use cases.

6. Retrieval Augmentation: Always provide relevant context to guide model responses.

7. What is prompt engineering and what are the best practices for writing effective prompts?

Prompt Engineering is the art of writing clear instructions for foundation models. Well-crafted prompts significantly improve output quality.

Best Practices:

1. Be Specific: Use detailed instructions rather than vague requests.

2. Provide Context: Include relevant background information.

3. Use Examples: Show the model example outputs you want.

4. Break Down Tasks: For complex tasks, break them into steps.

5. Specify Format: Request specific output formats or structures.

6. Set Constraints: Define length limits or prohibited content.

7. Iterate: Test and refine prompts based on results.

Example prompt: Instead of "Write about AWS," try "Write a 500-word guide introducing AWS to a startup CTO, focusing on cost benefits and scalability. Use a professional but conversational tone."

Related Article: Top Prompt Engineering Techniques

8. What are AI Agents in Amazon Bedrock and how do they differ from traditional chatbots?

AI Agents are autonomous systems that use foundation models to accomplish complex tasks. They can use tools, break down problems, and interact with external systems.

Agents Advantages over Chatbots:

  • Multi-step tasks: Agents plan and execute complex workflows

  • Tool integration: Agents call APIs and interact with external systems

  • Reasoning: Agents reason through problems step by step

  • Autonomy: Agents work independently without constant user guidance

  • Context retention: Agents maintain state across interactions

For example, an agent could book a flight by searching availability, checking prices, and completing payment. A chatbot would just answer questions about flights.

9. How would you implement role-based access control for Generative AI applications using AWS IAM?

Implement RBAC through:

1. Define Roles: Create IAM roles for different user groups (admin, developer, viewer).

2. Attach Policies: Define specific Bedrock permissions for each role.

3. Model Access Control: Restrict which models specific roles can invoke.

4. Guardrail Assignment: Apply different guardrails based on roles.

5. Audit Logging: Enable CloudTrail to track all API calls.

6. Resource Tags: Use tags to organize and control access to resources.

Example policy: Developers can invoke Claude models but not edit guardrails. Admins have full access.

10. What is vector search and which AWS services can be used to implement it?

Vector search finds similar items by comparing embeddings. It is fundamental to modern AI applications.

Implementation Options:

1. Bedrock Knowledge Bases: Managed vector search with built-in embedding generation.

2. OpenSearch Serverless: Fully managed vector database supporting semantic search.

3. Amazon Kendra: AI-powered search service with semantic understanding.

4. ElastiCache: Use Redis for fast vector similarity search.

Vector search enables semantic understanding rather than keyword matching. It powers recommendation engines, similarity search, and advanced retrieval.

AWS Serverless Interview Questions

Serverless computing is transforming application development. Master these concepts.

1. What is serverless computing, and how does it differ from traditional infrastructure?

Serverless computing abstracts infrastructure management. You write code and deploy it without managing servers.

AspectTraditionalServerless
Server ManagementManualAutomatic
ScalingManual or Auto ScalingAutomatic
PricingPer hour of runtimePer execution and resources used
DeploymentComplex provisioningSimple upload and deploy
MaintenanceYour responsibilityAWS responsibility

Serverless services include AWS Lambda, API Gateway, and DynamoDB.

2. What is Provisioned Concurrency in AWS Lambda, and how does it reduce cold starts?

Provisioned Concurrency keeps Lambda functions warm and ready. AWS keeps specified concurrency units initialized.

How it works:

  • AWS maintains specified number of function instances

  • Instances are fully initialized and ready to execute

  • New invocations immediately use these instances

  • No cold start delay for provisioned concurrency

Benefits:

  • Eliminates cold start latency

  • Provides consistent performance

  • Guarantees capacity for critical functions

Use Provisioned Concurrency for functions requiring sub-100ms latency.

Also Read: Top 10 AWS Alternatives For 2026

3. What is a cold start in AWS Lambda, and what strategies can be used to minimize it?

A cold start occurs when Lambda creates a new instance for the first time. The runtime initialization adds latency.

Minimize Cold Starts:

  • Use Provisioned Concurrency: Maintain warm instances ready for immediate use.

  • Use Efficient Runtimes: Python and Node.js start faster than Java.

  • Optimize Code Size: Reduce package size to speed up loading.

  • Use Layers: Pre-package dependencies to reduce initialization time.

  • Increase Memory: More memory allocates more CPU, speeding up initialization.

  • Scheduled Warmup: Periodically invoke functions to keep instances warm.

4. What are the common event sources that can trigger a Lambda function?

Lambda functions respond to various events:

  • API Gateway: HTTP requests from API endpoints

  • S3: Object creation, deletion, or updates

  • DynamoDB: Stream events from DynamoDB tables

  • SNS: Messages from SNS topics

  • SQS: Messages from SQS queues

  • CloudWatch: Scheduled events using cron expressions

  • Kinesis: Data stream events

  • EventBridge: Custom events and third-party service events

  • Cognito: Authentication events

Different event sources enable different use cases.

5. What is Amazon API Gateway, and how does it integrate with AWS Lambda?

API Gateway creates RESTful APIs that trigger Lambda functions. It provides HTTP endpoints that invoke Lambdas.

Integration:

  1. Create API in API Gateway

  2. Define resources and methods

  3. Configure Lambda integration

  4. Deploy API to stage

  5. API Gateway invokes Lambda for each request

Benefits:

  • HTTP request/response handling

  • Request validation

  • Authorization and authentication

  • Rate limiting and throttling

  • Caching responses

API Gateway + Lambda is the foundation of serverless web applications.

Also Read: What is Amazon Kinesis?

6. What is Amazon EventBridge, and how is it used in event-driven architectures?

EventBridge routes events between services. It connects event sources to event targets using rules.

Key Features:

  • Event routing: Route events based on patterns

  • Event transformation: Modify event structure before delivery

  • Dead letter queues: Handle failed events

  • Replay capability: Replay past events for reprocessing

EventBridge enables loose coupling between services. Services publish events without knowing consumers.

7. What are AWS Step Functions, and how do they help orchestrate serverless workflows?

Step Functions coordinate multiple Lambda invocations and other AWS services. They manage workflow execution, error handling, and retries.

Workflow Types:

Standard Workflows: Long-running workflows with full history.

Express Workflows: High-throughput, short-duration workflows.

Features:

  • Visual workflow designer

  • Built-in error handling and retries

  • Wait states and parallel execution

  • Human approval steps

  • Audit trail of all executions

Use Step Functions for complex serverless orchestration.

8. What is the difference between Amazon SNS and Amazon SQS in serverless architectures?

SNS (Simple Notification Service) and SQS (Simple Queue Service) serve different purposes:

AspectSNSSQS
DeliveryPush to subscribersPull from queue
PatternPub/SubQueue
SubscribersMultipleOne consumer at a time
PersistenceNot stored after deliveryMessages persist until consumed
LatencyLower (push)Higher (polling)
OrderingNo guaranteeFIFO available

Use SNS for broadcasting. Use SQS for buffering and processing.

9. How do you monitor and troubleshoot AWS Lambda functions using CloudWatch and AWS X-Ray?

CloudWatch Monitoring:

  • Logs: Lambda writes logs to CloudWatch Logs

  • Metrics: CPU, memory, and execution metrics

  • Alarms: Alert on error rates or duration

  • Dashboards: Visualize function performance

AWS X-Ray Tracing:

  • Trace requests: Follow requests across services

  • Service map: Visualize service dependencies

  • Latency analysis: Identify bottlenecks

  • Error analysis: Understand failure causes

Enable X-Ray tracing for end-to-end visibility.

Related Article: What is Okta?

10. How do you secure serverless applications in AWS using IAM, API Gateway, and encryption?

IAM Security:

  • Create specific roles for Lambda functions

  • Grant least privilege permissions

  • Use resource policies to control access

API Gateway Security:

  • Enable authentication (API keys, OAuth)

  • Use WAF for DDoS protection

  • Implement rate limiting

Encryption:

  • Encrypt environment variables

  • Use KMS for key management

  • Enable HTTPS on API endpoints

Implement multiple security layers for comprehensive protection.

Scenario-Based AWS Interview Questions

Real-world scenarios test your ability to apply knowledge practically. Here are some of them:

1. Your e-commerce application experiences a 15x traffic spike during a flash sale, causing downtime and slow AI-powered recommendations. How would you design a scalable and highly available AWS architecture to handle the load?

To handle a 15x traffic spike during a flash sale, I would design a highly available architecture using Amazon CloudFront to cache static content and reduce server load. The application would run behind an Application Load Balancer with Auto Scaling Groups deployed across multiple Availability Zones to automatically scale based on demand. I would use Amazon Aurora with read replicas for database scalability and Amazon ElastiCache (Redis) to cache frequently accessed data. AI-powered recommendations would be hosted on Amazon SageMaker endpoints with auto-scaling enabled. Additionally, Amazon SQS would be used to decouple backend processes such as order processing and notifications. This architecture ensures high availability, low latency, and seamless scalability during peak traffic events.

2. A critical application becomes unavailable due to an AWS regional outage. How would you implement a multi-region disaster recovery strategy with minimal downtime and data loss?

To minimize downtime and data loss during an AWS regional outage, I would implement a multi-region disaster recovery strategy. The application infrastructure would be deployed in a secondary AWS region, and Amazon Route 53 failover routing would automatically redirect traffic if the primary region becomes unavailable. For data replication, I would use Aurora Global Database or DynamoDB Global Tables and enable Amazon S3 Cross-Region Replication for object storage. Infrastructure would be managed using CloudFormation or Terraform so resources can be recreated quickly if needed. Regular backups through AWS Backup and continuous monitoring with CloudWatch would further strengthen recovery capabilities. This approach ensures business continuity with low Recovery Time Objective (RTO) and Recovery Point Objective (RPO).

3. Your company's AWS bill has increased by 50% because of EKS clusters, AI workloads and idle resources. How would you identify and optimize cloud costs without affecting performance?

If the AWS bill increased significantly, I would first analyze spending using AWS Cost Explorer, Cost and Usage Reports, AWS Budgets, and Compute Optimizer to identify the primary cost drivers. For EKS workloads, I would rightsize worker nodes, enable Cluster Autoscaler, use Karpenter for efficient provisioning, and leverage Spot Instances where appropriate. For AI workloads, I would optimize SageMaker endpoint scaling, shut down idle notebook instances, and schedule non-production resources to run only when needed. I would also identify unused resources such as unattached EBS volumes, idle load balancers, and unused Elastic IPs. Finally, I would evaluate Savings Plans and Reserved Instances for predictable workloads. This strategy reduces cloud costs while maintaining application performance and reliability.

4. A public-facing API is facing DDoS attacks, unauthorized access attempts and suspicious login activity. How would you secure the environment using AWS security services and Zero Trust principles?

To secure the environment, I would adopt a Zero Trust security model where no user or request is trusted by default. I would use AWS Shield Advanced and Amazon CloudFront to protect against DDoS attacks and configure AWS WAF with rate limiting, bot protection, and rules to block SQL injection and cross-site scripting attacks. APIs would be placed behind Amazon API Gateway with request throttling, authentication, and authorization controls. IAM policies would follow the principle of least privilege, and Multi-Factor Authentication would be enforced for all privileged users. For threat detection and monitoring, I would enable Amazon GuardDuty, Security Hub, Amazon Inspector, CloudTrail, and CloudWatch. This layered security approach protects the API from external threats while providing continuous visibility into suspicious activities.

5. A legacy monolithic application on EC2 is difficult to scale and maintain. How would you modernize it using AWS cloud-native services while minimizing migration risks?

To modernize a legacy monolithic application, I would follow a phased migration approach to minimize risk. Initially, I would containerize the application using Docker and deploy it on Amazon ECS or EKS to improve scalability and deployment flexibility. Using the Strangler Pattern, I would gradually extract individual components such as authentication, product management, and notifications into independent microservices. Event-driven workloads could be moved to AWS Lambda, Amazon EventBridge, and Amazon SQS for greater scalability and reduced operational overhead. Database migration would be handled using AWS Database Migration Service, while CI/CD pipelines would be implemented using AWS CodePipeline, CodeBuild, and CodeDeploy. This incremental modernization strategy improves scalability, maintainability, and deployment speed without disrupting existing business operations.

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About the Author
Priyanka Sharma
About the Author

Priyanka Sharma has spent over a decade in cloud infrastructure, helping organizations migrate legacy systems to AWS, Azure, and Google Cloud. She designs scalable architectures for mid-sized enterprises and troubleshoots production environments under real deployment pressure. She tests new tools firsthand, turning client engagements into practical steps IT teams can apply immediately.

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