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 resources on-demand from a cloud provider and pay based on usage.
Core components of IaaS
IaaS typically exposes the following building blocks as services:
- Virtual Machines (compute)
- Block and object Storage
- Virtual Networks (VPCs, subnets, routing)
- Load balancers and IP addressing
- Identity and access management (IAM)
- Monitoring, logging, and basic orchestration tools
How it differs from PaaS and SaaS
– SaaS (Software as a Service): Delivers complete applications (e.g., Salesforce, Gmail). Users manage little to nothing.
– PaaS (Platform as a Service): Provides an application platform (runtime, middleware) where developers deploy code without managing the underlying infrastructure (e.g., Heroku, Google App Engine).
– IaaS: Gives maximum control over OS, runtime, and middleware because you manage VMs, storage, and network while the provider manages physical data center and virtualization.
Common use-cases
- Lift-and-shift migrations of on-premises workloads to the cloud
- Development and test environments with fast provisioning
- High-performance computing and batch processing
- Disaster recovery and backup systems
- Running custom software stacks or legacy applications that need OS-level control
Advantages
- Scalability: Spin up/down resources on-demand.
- Cost efficiency: Pay-as-you-go model reduces capital expenditure.
- Speed: Faster provisioning compared to buying hardware.
- Flexibility: Full control of operating system and middleware.
Drawbacks and considerations
- Responsibility: You must manage OS patches, security hardening, and application deployments.
- Complexity: More operational overhead than PaaS/SaaS.
- Cost surprises: Poorly optimized resources can lead to higher bills.
Security and compliance
With IaaS, the provider secures the physical infrastructure and virtualization layer, while the customer is responsible for securing guest OS, applications, data, and IAM policies. Ensure proper network segmentation, encryption at rest/in transit, logging, and regular patching.
Examples of IaaS providers
- AWS EC2, EBS, VPC
- Microsoft Azure Virtual Machines, Managed Disks, Virtual Network
- Google Cloud Compute Engine, Persistent Disk, VPC
Quick CLI example (AWS)
aws ec2 run-instances --image-id ami-0abcdef1234567890 --count 1 --instance-type t3.medium --key-name MyKeyPair --subnet-id subnet-12345678
Interview tip
When asked “What is IaaS?” in an interview, keep the definition concise, mention a few core components, contrast it with PaaS/SaaS, and give a real-world use-case. If you have hands-on experience, briefly describe a migration or provisioning task you performed.
Keywords: IaaS, Infrastructure as a Service, cloud computing, AWS EC2, Azure VM, GCP Compute Engine