The Ultimate Cloud Engineering Interview Guide (AWS & Azure)

Cloud Engineering and DevOps roles are highly specialized. You are expected to understand networking, infrastructure as code (IaC), container orchestration, and security across distributed systems.

This guide breaks down the core concepts you will be tested on in any AWS or Azure interview.

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Theme 1: Core Compute and Serverless

1. "Explain the difference between EC2, ECS, and Lambda (AWS)."

• EC2 (Elastic Compute Cloud): Infrastructure as a Service (IaaS). You manage the OS, patching, and scaling. Use for legacy apps.
• ECS (Elastic Container Service): Container as a Service (CaaS). You package your app in Docker. AWS manages the clustering.
• Lambda: Function as a Service (FaaS) / Serverless. You just write code. AWS spins up the environment on-demand and charges per millisecond. Use for event-driven architectures.

2. "What are the trade-offs of going fully Serverless?"

• Pros: Zero server maintenance, auto-scaling, pay-per-execution.
• Cons: Cold starts (latency when a function is invoked after being idle), vendor lock-in, and difficult local debugging.

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Theme 2: Networking and Security

3. "Design a secure VPC architecture for a 3-tier web app."

You must understand VPCs, Subnets, and NAT Gateways.

• Public Subnet: Contains the Application Load Balancer (ALB) and Bastion Host. It has an Internet Gateway (IGW).
• Private Subnet 1 (App Tier): Contains the EC2 instances/Containers running the web servers. They access the internet via a NAT Gateway.
• Private Subnet 2 (Data Tier): Contains the RDS Database. Completely isolated. Only accepts traffic from the App Tier's Security Group.

4. "What is the difference between a Security Group and a Network ACL?"

• Security Group: Operates at the instance level. It is stateful (if you allow an inbound request, the outbound response is automatically allowed).
• Network ACL: Operates at the subnet level. It is stateless (you must explicitly define both inbound and outbound rules).

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Theme 3: Infrastructure as Code (IaC)

5. "Why use Terraform over AWS CloudFormation?"

• Terraform: Cloud-agnostic (supports AWS, Azure, GCP). Uses HCL (HashiCorp Configuration Language). Maintains state locally or remotely (S3).
• CloudFormation: AWS-specific. Uses JSON/YAML. Better deep integration for niche AWS services, but locks you into the AWS ecosystem.

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Theme 4: High Availability & Disaster Recovery

6. "How do you achieve High Availability (HA) in the cloud?"

• Deploy instances across multiple Availability Zones (AZs).
• Use an Auto Scaling Group (ASG) attached to a Load Balancer to automatically replace unhealthy instances.
• Use Multi-AZ RDS for synchronous database replication to a standby instance.

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Conclusion

Cloud interviews are heavily focused on practical architecture. They don't want you to just define terms; they want to know when to use DynamoDB vs RDS, or when to use Kubernetes vs ECS. Practice drawing VPC diagrams and use InterviPrep AI to simulate architectural deep dives.