Quick definition
Infrastructure as a Service (IaaS) is a cloud computing model that provides virtualized computing resources over the internet. Instead of owning physical servers, storage, or networking hardware, organizations rent these resources on-demand from a cloud provider and manage operating systems, applications, and data themselves.
Core components
IaaS typically includes:
– Virtual machines (compute instances)
– Virtual networking (VPCs, subnets, load balancers)
– Block and object storage
– Security controls (firewalls, security groups)
– Optional services like IP addresses, monitoring, and snapshots
How IaaS works
Cloud providers run large data centers with physical servers and networking hardware. They use virtualization and orchestration layers to present virtual resources (VMs, virtual disks, virtual networks) to customers. Users provision and scale resources using web consoles, APIs, SDKs, or CLI tools.
Benefits of IaaS
– Cost efficiency: pay-as-you-go pricing avoids large capital expenditure on hardware.
– Scalability: scale compute, storage, and networking up or down in minutes.
– Speed & agility: quickly provision environments for development, testing, and production.
– Global reach: cloud providers offer regions and availability zones for geographic redundancy.
Common use cases
– Hosting legacy applications that need full OS access
– Development and testing environments
– High-performance computing and batch processing
– Disaster recovery and backup solutions
– Running custom middleware, databases, and container orchestration platforms
Examples of IaaS providers
– Amazon Web Services (AWS) — EC2, EBS, VPC
– Microsoft Azure — Virtual Machines, Managed Disks, Virtual Network
– Google Cloud Platform (GCP) — Compute Engine, Persistent Disk, VPC
IaaS vs PaaS vs SaaS
– IaaS: Provider manages the underlying infrastructure; you manage OS, middleware, applications, and data.
– PaaS: Provider also manages the runtime and middleware; you deploy applications without worrying about OS-level management.
– SaaS: Provider delivers fully managed applications; you only use the software (e.g., email, CRM).
Security and compliance considerations
With IaaS, responsibility is shared: the provider secures the physical infrastructure and hypervisor, while customers are responsible for secure configuration of VMs, OS patches, application-level security, encryption of data at rest and in transit, and identity/access management.
Pricing models
– On-demand: pay for resources by the hour or second without commitment.
– Reserved or committed use: discounted prices for long-term commitments.
– Spot/preemptible instances: lower-cost compute for interruptible workloads.
Quick example: launch an EC2 instance using AWS CLI
aws ec2 run-instances --image-id ami-0abcdef1234567890 --count 1 --instance-type t3.medium --key-name MyKeyPair --subnet-id subnet-12345678 --security-group-ids sg-12345678
Terraform snippet (basic EC2 instance)
provider "aws" {
region = "us-east-1"
}
resource "aws_instance" "web" {
ami = "ami-0abcdef1234567890"
instance_type = "t3.medium"
tags = { Name = "example-web" }
}
Interview tip
When answering “What is IaaS?” in an interview, keep your response concise: define IaaS, highlight the shared responsibility model, provide 1–2 common examples, and mention a relevant use case or pricing model. Demonstrating familiarity with real cloud providers (AWS, Azure, GCP) scores well.