Quick definition
IaaS (Infrastructure as a Service) is a cloud computing model that provides virtualized computing resources over the internet. Instead of purchasing and managing physical servers, storage, and networking equipment, organizations rent those resources from a cloud provider on a pay-as-you-go basis.
Core components (what IaaS delivers)
Typical IaaS offerings include:
- Virtual machines (compute) — scalable VMs with configurable CPU, memory, and OS.
- Block and object storage — persistent volumes for VMs and object stores for files and backups.
- Networking — virtual networks, load balancers, IP addressing, and firewalls.
- Identity and access management — user/role controls and API keys.
Popular examples
Major IaaS providers and services:
- AWS EC2, EBS, VPC
- Microsoft Azure Virtual Machines, Azure Storage, Azure Virtual Network
- Google Compute Engine (GCE), Google Cloud Storage, Google VPC
- DigitalOcean Droplets, Backblaze B2 (storage)
IaaS vs PaaS vs SaaS (short comparison)
In cloud model comparisons, the level of control vs managed responsibility shifts:
- IaaS: You manage applications, middleware, and OS; provider manages underlying virtualization, servers, storage, and networking.
- PaaS: Provider manages OS and runtime; you deploy and manage applications only.
- SaaS: Provider manages everything; you just use the application.
Benefits of IaaS
- Scalability — quickly scale compute and storage up/down.
- Cost-efficiency — pay only for resources used; no capital expenditure for hardware.
- Faster provisioning — deploy environments in minutes.
- Flexibility — choose OS, middleware, and configuration to match requirements.
Drawbacks / considerations
- Operational overhead — you’re responsible for OS patching, middleware, backups, and security configuration.
- Potential cost surprises — poor resource management can increase bills.
- Vendor lock-in risk — some services or tooling may be platform-specific.
Common use cases
- Lift-and-shift migrations of on-prem apps to cloud VMs.
- Test and development environments that need rapid provisioning.
- Hosting legacy applications that require custom OS or middleware.
- High-performance computing and batch processing.
Interview-ready answer (concise)
“IaaS, or Infrastructure as a Service, is a cloud model where a provider supplies virtualized compute, storage, and networking resources over the internet. It lets organizations rent infrastructure on-demand—examples include AWS EC2, Azure VMs, and Google Compute Engine. Compared with PaaS and SaaS, IaaS gives the most control over the operating system and middleware but requires you to manage and secure them. It’s ideal for lift-and-shift migrations, custom environments, and scalable test/dev workloads.”
Example CLI snippets
Launch a small VM on AWS using the AWS CLI (example):
aws ec2 run-instances --image-id ami-0123456789abcdef0 --count 1 --instance-type t3.small --key-name my-key --subnet-id subnet-abcde123 --security-group-ids sg-01234567
Key keywords to use in your answer
IaaS, Infrastructure as a Service, virtual machines, compute, block storage, object storage, VPC, scalability, pay-as-you-go, cloud migration.
Further reading
Refer to provider docs: AWS EC2 documentation, Azure Virtual Machines docs, and Google Compute Engine docs for hands-on examples and best practices.