---
term: 'Infrastructure-as-a-Service (IaaS)'
seoTitle: 'What is IaaS (Infrastructure-as-a-Service)? Complete Guide'
headline: 'What is Infrastructure-as-a-Service (IaaS)?'
slug: infrastructure-as-a-service
category: cloud-architecture
shortDefinition: 'IaaS is a cloud model that rents fundamental computing resources — virtual machines, storage, networking — on demand, billed as you go.'
relatedTerms:
  - paas-vs-baas
  - baas-vs-custom-backend
  - multi-tenant-cloud-hosting
  - cloud-vendor-lock-in
  - iaas-paas-baas-faas
contrastsWith:
  - paas-vs-baas
faq:
  - question: 'What is IaaS in simple terms?'
    answer: 'Renting computers instead of buying them. An IaaS provider owns the data centers, physical servers, and networking; you rent virtual machines, storage, and networks by the hour and manage everything from the operating system up. Capital expense becomes operating expense, and provisioning takes minutes instead of procurement cycles.'
  - question: 'What does the provider manage versus the customer in IaaS?'
    answer: 'The provider runs the physical layer: data centers, servers, storage hardware, networking, and the virtualization that slices it into rentable units. You run everything above the hypervisor: operating system, patching, runtime, middleware, applications, and data. Under the shared-responsibility model, the provider secures the cloud; you secure what you put in it.'
  - question: 'Is IaaS the same as virtualization?'
    answer: 'No — virtualization is the enabling technology, IaaS is the business model built on it. Hypervisors slice physical machines into virtual ones; IaaS wraps that in self-service, metering, and pay-as-you-go delivery over the internet. You can run virtualization in your own basement; it becomes IaaS when someone rents it to you as a service.'
  - question: 'What is the difference between IaaS and PaaS?'
    answer: 'The management line. IaaS hands you raw infrastructure and everything from the OS up is your job — maximum control, maximum operational burden. PaaS also manages the OS, runtime, and middleware, so you bring only application code and data. Choose IaaS for control and custom stacks; choose PaaS to ship faster with less ops.'
  - question: 'What are the main benefits of IaaS?'
    answer: 'Elastic capacity that scales with demand, provisioning in minutes, the shift from up-front hardware purchases to pay-as-you-go, geographic reach without building data centers, and built-in options for redundancy and disaster recovery. The common thread: infrastructure decisions become reversible, which physical hardware never was.'
  - question: 'What are the disadvantages of IaaS?'
    answer: 'The honest list vendors skip: bills that climb when unused resources run idle, egress fees for moving data out, security misconfiguration as the leading cause of cloud breaches, an operational skill set you must hire or grow, and vendor lock-in through proprietary adjacent services. IaaS removes the hardware, not the operations.'
  - question: 'When should you NOT use IaaS?'
    answer: 'When you would only be rebuilding what a higher abstraction already provides. A standard application backend — users, data, storage, APIs — assembled by hand on rented VMs means weeks of undifferentiated setup that a PaaS or BaaS delivers in minutes. IaaS earns its keep for custom stacks, legacy migrations, and compliance-driven control; for standard workloads it is usually the expensive way to get there.'
  - question: 'Is IaaS public, private, or hybrid?'
    answer: 'All three deployments exist. Public IaaS pools many customers on shared hardware — the standard, cheapest form. Private IaaS dedicates infrastructure to one organization for control or compliance. Hybrid mixes both, keeping sensitive workloads private while bursting to public capacity. The service model is the same; the tenancy differs.'
codeLanguages: [javascript, dart, swift, kotlin]
externalAuthorities:
  - name: 'The NIST Definition of Cloud Computing (SP 800-145)'
    url: 'https://csrc.nist.gov/pubs/sp/800/145/final'
  - name: 'Infrastructure as a service (Wikipedia)'
    url: 'https://en.wikipedia.org/wiki/Infrastructure_as_a_service'
  - name: 'Serverless Architectures — Mike Roberts (martinfowler.com)'
    url: 'https://martinfowler.com/articles/serverless.html'
  - name: 'Back4app documentation'
    url: 'https://www.back4app.com/docs'
cta:
  title: 'Skip the infrastructure entirely'
  text: 'Back4app sits four rungs above raw VMs: database, auth, storage, and APIs arrive pre-built and managed, with Cloud Code for custom logic. Get what you would have spent weeks assembling on IaaS — in minutes, free.'
  linkText: 'Start Free'
  linkUrl: 'https://www.back4app.com/signup'
author: 'Back4app Engineering'
publishedDate: '2026-07-24'
translationKey: infrastructure-as-a-service
---

**IaaS is a cloud model that rents fundamental computing resources — virtual machines, storage, networking — on demand, billed as you go.** The [NIST definition](https://csrc.nist.gov/pubs/sp/800/145/final) draws the boundary precisely: the provider controls the physical infrastructure; you control operating systems, storage, and deployed applications. It is the bottom rung of the cloud ladder — the one that replaces buying servers with renting them.

## Key takeaways

| Question | Answer |
| --- | --- |
| What it is | On-demand virtual machines, storage, and networks — hardware as a utility |
| What you still do | Everything from the operating system up: patch, secure, scale, operate |
| Problem it solves | Buying, racking, and depreciating physical hardware |
| Billing model | Per resource-hour — flexible, and unforgiving of idle waste |
| The honest caveat | IaaS removes the hardware, not the operations |

## What using IaaS looks like

The signature experience is a machine in minutes — followed by everything a machine has always needed:

```bash
# Minute one: rent the machine
$ cloud compute create --size medium --image ubuntu-24.04
   ✓ vm-7f3a running — 203.0.113.40

# Minute two onward: everything is still your job
$ ssh admin@203.0.113.40
$ apt update && apt upgrade          # patching: yours
$ apt install nginx postgresql       # stack: yours
$ ufw allow 443 && configure-tls…    # security: yours
$ crontab -e                         # backups, rotation, monitoring: yours
```

That trade — hardware in minutes, operations forever — is the whole model. For contrast, here is the same "get a backend running" goal at the top of the ladder, where the infrastructure never surfaces at all:

**JavaScript:**

```javascript
// JavaScript / Node.js — Back4app JS SDK
const note = new Parse.Object('Note');
note.set('text', 'Shipped without touching a VM');
await note.save(); // no instance sized, no OS patched, no firewall rules
```

**Flutter:**

```dart
// Flutter / Dart — Back4app Flutter SDK
final note = ParseObject('Note')
  ..set('text', 'Shipped without touching a VM');
await note.save(); // no instance sized, no OS patched
```

**Swift:**

```swift
// iOS / Swift — Back4app Swift SDK
var note = Note()
note.text = "Shipped without touching a VM"
note.save { result in
  if case .success = result { print("saved — zero infrastructure managed") }
}
```

**Kotlin:**

```kotlin
// Android / Kotlin — Back4app Android SDK
val note = ParseObject("Note").apply {
  put("text", "Shipped without touching a VM")
}
note.saveInBackground { e ->
  if (e == null) Log.d("Note", "saved — zero infrastructure managed")
}
```

## Who manages what

```mermaid
flowchart LR
  accTitle: The IaaS responsibility split
  accDescr: The provider manages data centers, physical servers, storage, networking, and virtualization; the customer manages the operating system, runtime, applications, and data on top.
  subgraph P["Provider runs"]
    p1["Data centers · physical servers<br/>storage · network · virtualization"]
  end
  subgraph Y["You run"]
    y1["OS · patching · runtime<br/>middleware · apps · data"]
  end
  P --> Y
```

This split is also the security model: the provider secures *the cloud*, you secure everything *in* it. Misconfiguration on the customer side — open storage buckets, permissive firewall rules, unpatched systems — is the leading cause of cloud breaches, which is why the "you run" box deserves more respect than it usually gets.

## IaaS vs. PaaS vs. BaaS vs. on-premises

| Dimension | On-premises | IaaS | PaaS | BaaS |
| --- | --- | --- | --- | --- |
| You buy/rent | Hardware | Virtual infrastructure | A managed platform | A managed backend |
| You manage | Everything | OS and up | App + data | Custom logic + data |
| Provisioning time | Weeks–months | Minutes | Minutes | Minutes, backend included |
| Cost shape | Capital expense | Per resource-hour | Per instance/tier | Free tier + plans |
| Control | Total | High | Medium | Low, by design |
| Ops burden | Total | High | Low | Minimal |

One clarification that recurs in every "IaaS vs." discussion: [serverless models](https://martinfowler.com/articles/serverless.html) aren't a fourth column of the same kind — they abstract the *unit of compute* (per-invocation) rather than the *layer of management*, which is why a serverless platform can itself run on IaaS underneath.

## Common use cases

- **Lift-and-shift migrations.** Existing server applications move to rented VMs mostly unchanged — same stack, no more hardware refresh cycles.
- **Custom and legacy stacks.** Unusual runtimes, licensed software, or OS-level tuning that managed platforms won't allow.
- **Compliance-driven control.** Regimes that require knowing and configuring exactly what runs beneath the application.
- **High-performance and specialized workloads.** GPU fleets, large-scale data processing, and anything with hardware-shaped requirements.
- **Disaster recovery and burst capacity.** Standby environments and traffic-spike headroom that would be ruinous to own as idle hardware.

## Should you build on IaaS? A decision matrix

| Choose IaaS when… | Choose a higher rung when… |
| --- | --- |
| You need OS-level control or custom stacks | The backend needs are standard (users, data, files, APIs) |
| A capable ops team already exists | The team is developers-only |
| Migrating existing server workloads as-is | Building something new from zero |
| Compliance dictates infrastructure control | Time-to-market dominates every other concern |
| Sustained scale makes raw unit prices decisive | The workload is small, spiky, or exploratory |

The pattern worth internalizing: IaaS is rarely wrong for *moving* existing systems, and rarely right for *starting* standard ones — a new app backend assembled by hand on VMs is weeks of work that higher rungs deliver before lunch.

## Limitations and trade-offs

- **Operations remain yours.** Patching, hardening, scaling, backups, monitoring — the runbook survives intact; only the hardware under it changed.
- **Bill shock is a skill issue you inherit.** Idle instances, oversized VMs, and forgotten storage bill around the clock; cost management becomes an ongoing discipline.
- **Egress is the exit toll.** Data flows in free and out at a price — a mechanism that quietly compounds into [cloud vendor lock-in](https://en.wikipedia.org/wiki/Vendor_lock-in) as data accumulates.
- **Security misconfiguration is the top failure mode.** The provider's half of shared responsibility is excellent; breaches overwhelmingly happen in the customer's half.
- **The skills tax.** Running infrastructure well requires people who run infrastructure well — a hiring requirement the pay-as-you-go pricing page doesn't mention.

## Where Back4app stands relative to IaaS

Back4app is an open-source Backend-as-a-Service (BaaS) platform that combines a managed database, auto-generated REST and GraphQL APIs, authentication, file storage, and Cloud Code serverless functions. Relative to IaaS, it is the opposite end of the trade: no OS access, no infrastructure control — and no runbook, because the entire "you run" box from the diagram above is the platform's job. Teams that need raw infrastructure for one specialized workload can run it beside a BaaS backend; teams building standard app backends can skip the bottom rung entirely. And because the stack is open source, descending the ladder later — self-hosting the platform on IaaS you control — remains a real option, not a rewrite.