What is IaaS? (Infrastructure as a Service) — Interview Answer

Quick definition

Infrastructure as a Service (IaaS) is a cloud computing model that provides virtualized computing resources over the internet. Instead of buying and managing physical servers, storage, and networking hardware, organizations rent these components from a cloud provider on a pay-as-you-go basis.

Core components of IaaS

IaaS typically includes:

Virtual machines (VMs) or compute instances
Block and object storage
Virtual networks, subnets, and load balancers
Identity and access management (IAM)
Monitoring, backup and basic security services

How IaaS works

Cloud providers run large-scale data centers and expose APIs or consoles that let customers provision and manage infrastructure resources programmatically. Users choose the instance type, OS, storage size, and networking configuration, and the provider allocates the virtual resources.

Common examples

Major IaaS providers include:

AWS EC2, EBS, VPC
Microsoft Azure Virtual Machines, Managed Disks, Virtual Network
Google Cloud Compute Engine, Cloud Storage, VPC

Benefits

Key advantages of IaaS:

Scalability — quickly add/remove compute and storage
Cost-effective — pay only for what you use, lower capital expenditure
Flexibility — choose OS, middleware, and applications
Faster provisioning — deploy infrastructure in minutes

Typical use cases

IaaS is well-suited for:

Testing and development environments
Web and application hosting
High-performance computing and big data workloads
Disaster recovery and backup
Migrating legacy applications to the cloud

IaaS vs PaaS vs SaaS (short comparison)

Understanding the shared responsibility and management scope helps when choosing a model:

IaaS: You manage OS, runtime, middleware and apps; provider manages virtualization, servers, storage, networking.
PaaS: Provider manages OS and runtime; you deploy applications only.
SaaS: Provider delivers fully managed software; you just use the application.

Security & cost considerations

Although IaaS reduces hardware overhead, teams must secure their OS, applications and configurations. Cost management requires monitoring instance sizes, reserved instances, and idle resources to avoid surprises.

Interview-ready answer (concise)

“IaaS, or Infrastructure as a Service, is a cloud model that provides virtualized computing resources—such as VMs, storage and networking—on demand. It lets organizations avoid capital expenditure on physical servers, scale quickly, and pay only for used resources. IaaS requires you to manage the OS and applications while the provider manages the underlying physical infrastructure.”