Top Cloud Computing Interview Questions (2026 Guide)

Q1: Explain the differences between IaaS, PaaS, and SaaS.

A: This is a fundamental concept in cloud delivery models:

• IaaS (Infrastructure as a Service): The provider offers basic computing resources (VMs, networking, storage). You manage the OS, runtime, and applications (e.g., AWS EC2).
• PaaS (Platform as a Service): Provides a platform allowing customers to develop, run, and manage applications without dealing with infrastructure (e.g., Heroku, Google App Engine).
• SaaS (Software as a Service): Delivers fully functional applications over the internet (e.g., Google Workspace, Salesforce).

Q2: What is the difference between Public, Private, and Hybrid clouds?

A: Cloud deployment models dictate where data is hosted:

• Public Cloud: Services are offered over the public internet and available to anyone (e.g., AWS, Azure). It's cost-effective but offers less customization.
• Private Cloud: Infrastructure operated solely for a single organization, offering higher security and control.
• Hybrid Cloud: Combines both public and private clouds, allowing data and applications to be shared between them for greater flexibility and optimization.

Q3: How do you design a highly available architecture?

A: Designing for high availability involves eliminating single points of failure. Key strategies include:

• Deploying resources across multiple Availability Zones (AZs) or Regions to ensure geographic redundancy.
• Using Elastic Load Balancers (ELB) to distribute incoming traffic evenly across healthy instances.
• Implementing Auto Scaling to automatically adjust compute capacity based on demand.
• Utilizing managed, multi-AZ database services (e.g., Amazon RDS Multi-AZ).

Q4: How do AWS S3, Azure Blob, and Google Cloud Storage compare?

A: All three are object storage services designed for high durability and scalability. They are accessed via RESTful APIs and offer tiered storage classes (e.g., Standard, Infrequent Access, Cold Storage). The main differences lie in pricing structures, specific integration with their respective ecosystems, and lifecycle management nuances.

Q5: Explain Serverless Computing and give an example.

A: Serverless computing allows developers to build and run applications without managing the underlying infrastructure. The cloud provider automatically provisions, scales, and manages the infrastructure required to run the code. You only pay for the compute time consumed.

Example: AWS Lambda, Azure Functions, or Google Cloud Functions executing code in response to events like an image upload to an S3 bucket.

Q6: What is the Shared Responsibility Model?

A: It defines the security obligations of the cloud provider and the customer. Generally, the provider is responsible for the "security OF the cloud" (physical infrastructure, host OS, network), while the customer is responsible for "security IN the cloud" (customer data, application security, identity and access management). Always remember to configure your firewalls (like AWS Security Groups) and IAM roles correctly!

Q7: Your company’s cloud bill spiked by 40% last month. How do you investigate and resolve this?

A: I would start by analyzing billing dashboards (e.g., AWS Cost Explorer). I'd look for anomalies in specific services or regions. Common culprits include:

• Unattached or orphaned resources (e.g., EBS volumes, Elastic IPs).
• Over-provisioned instances running at low utilization.
• Unexpected data transfer out (egress) costs.

To resolve it, I would set up billing alarms, implement resource tagging for better tracking, and use tools like AWS Trusted Advisor to find optimization opportunities. Additionally, writing a Python script using Boto3 to automatically shut down non-production environments during off-hours can save significant costs.