Definition
Cloud computing is the delivery of computing services — including servers, storage, databases, networking, software, analytics, and intelligence — over the internet (“the cloud”) to offer faster innovation, flexible resources, and economies of scale. Users pay only for cloud services they use, helping lower operating costs and run infrastructure more efficiently.
Core characteristics
Cloud platforms typically offer:
- On-demand self-service — provision resources without human interaction.
- Broad network access — services available over the internet.
- Resource pooling — providers serve multiple customers using shared resources.
- Rapid elasticity — scale resources up or down quickly.
- Measured service — pay-per-use metering and billing.
Service models
There are three primary service models you should know for interviews:
- IaaS (Infrastructure as a Service) — provides virtualized compute, storage, and networking (e.g., Amazon EC2, Google Compute Engine).
- PaaS (Platform as a Service) — provides a platform to develop, run, and manage applications without managing underlying infrastructure (e.g., Heroku, Google App Engine).
- SaaS (Software as a Service) — delivers software applications over the internet on a subscription basis (e.g., Salesforce, Office 365).
Deployment models
Common deployment models include:
- Public cloud — services offered over the public internet and available to anyone (e.g., AWS, Azure, GCP).
- Private cloud — cloud environment dedicated to a single organization, hosted on-premises or in a provider’s data center.
- Hybrid cloud — combination of public and private clouds, enabling workload portability and data integration.
- Multi-cloud — using multiple cloud providers to avoid vendor lock-in or to take advantage of best-of-breed services.
Simple example (CLI)
Example: launching a virtual machine in AWS using the AWS CLI:
aws ec2 run-instances --image-id ami-0abcdef1234567890 --count 1 --instance-type t3.micro --key-name mykey
Benefits
- Cost efficiency — reduce capital expenditures and pay only for what you use.
- Scalability — handle traffic spikes by autoscaling resources.
- Speed & agility — faster deployment cycles and innovation.
- Reliability — built-in redundancy and global availability zones.
Challenges & considerations
Key concerns when adopting cloud include security, compliance, data governance, cost management, and potential vendor lock-in. Organizations should plan architecture, identity/access management, encryption, and monitoring properly.
Interview tip: concise answer
Start with a 1–2 sentence definition, mention service and deployment models, and finish with one or two benefits. Example:
"Cloud computing is delivering computing resources over the internet on a pay-as-you-go basis. Common models are IaaS, PaaS, and SaaS; deployment can be public, private, or hybrid. It provides scalability, cost savings, and faster time-to-market."
Common use-cases
- Web & mobile application hosting
- Data analytics and big data processing
- Disaster recovery & backup
- CI/CD pipelines and developer sandboxes
Understanding cloud fundamentals and being able to map a business problem to a service model (IaaS/PaaS/SaaS) will help you stand out in interviews.