AWS Cloud Interview Master
Curated 20+ essential AWS questions covering EC2, S3, VPC networking, IAM security, Serverless Lambda, and database architectures.
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What is AWS, and what is the difference between Regions and Availability Zones (AZs)?
AWS (Amazon Web Services) is a comprehensive cloud computing platform. An AWS Region is a geographical area (like us-east-1) containing multiple data center clusters. An Availability Zone (AZ) is one or more discrete data centers with redundant power, networking, and connectivity within an AWS Region. High availability is achieved by deploying applications across multiple AZs.
What is Amazon EC2, and what are its different instance pricing models?
Amazon EC2 (Elastic Compute Cloud) provides secure, resizable compute capacity in the cloud. Pricing models include:
1. On-Demand: Pay by the second/hour, no commitment. Best for short-term, unpredictable workloads.
2. Reserved Instances (RIs): Commit to 1-3 years for up to 72% discount. Best for steady-state workloads.
3. Savings Plans: Commit to hourly spend for discounts across EC2/Fargate/Lambda.
4. Spot Instances: Bid on spare AWS capacity for up to 90% discount. Can be terminated by AWS with 2 min warning. Best for fault-tolerant, batch jobs.
What is Amazon S3, and what are its storage classes?
Amazon S3 (Simple Storage Service) is an object storage service offering industry-leading scalability and durability. Storage classes include:
1. S3 Standard: For active, frequently accessed data.
2. S3 Intelligent-Tiering: Automatically moves data to cost-optimal tier based on access patterns.
3. S3 Standard-IA: For infrequently accessed data that requires rapid access.
4. S3 One Zone-IA: Lower cost IA stored in a single AZ (less resilient).
5. S3 Glacier (Instant, Flexible, Deep Archive): Low-cost archiving, retrieval times range from minutes to 12 hours.
What is AWS IAM, and what are its core components?
Explain the difference between a Security Group and a Network Access Control List (NACL).
What is an Application Load Balancer (ALB) vs a Network Load Balancer (NLB)?
What is serverless computing, and how does AWS Lambda work?
What is Amazon VPC?
What is the difference between Public Subnets and Private Subnets in a VPC?
What is AWS Auto Scaling?
What is Amazon RDS, and how does it support high availability?
What is Amazon DynamoDB?
Explain the purpose of Amazon Route 53.
What is AWS CloudFront?
What is the difference between AWS CloudTrail and Amazon CloudWatch?
What is the AWS Shared Responsibility Model?
What is Infrastructure as Code (IaC), and how is it used in AWS?
What is a Cold Start in AWS Lambda, and how do you reduce it?
Explain the difference between SQS and SNS.
How do you securely connect an on-premise network to an AWS VPC?
Technical Interview Mastery Blueprint
Proven methodologies and frameworks to succeed in technical and architecture rounds.
1. The Engineering STAR Technique
When responding to architectural or situational questions, structure your answer using Situation, Technical Constraint, Action, and Measurable Result. Rather than jumping straight to syntax, articulate the business problem, why certain patterns (e.g. caching, queuing, immutability) were selected over alternatives, and what latency or throughput improvements were achieved.
2. Defending Architectural Trade-Offs
Senior interviewers evaluate how you weigh trade-offs. Always explain why you chose an approach: e.g., memory overhead vs CPU cycle speed, consistency vs availability (CAP theorem), or normalized schemas vs denormalized fast reads. Stating the drawbacks of your own proposal demonstrates maturity and production experience.
3. Clean Code & Edge-Case Proactivity
In live-coding rounds, communicate your thinking aloud before typing. State edge cases explicitly: null or undefined inputs, extreme boundary values, concurrency races, and network timeouts. Writing modular, well-named functions with deterministic unit tests separates junior candidates from staff-level engineers.
4. Antipatterns to Avoid
Avoid reciting memorized definitions without practical context. Never dismiss non-functional requirements such as security (CSRF, injection, token rotation), observability (logging, metrics), and accessibility (ARIA, semantic standards). Always ask clarifying scope questions before writing complex implementations.
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