Cloud Computing Models

Also Known As

TL;DR

Explanation

IaaS (EC2, GCE): raw VMs — you manage OS, runtime, and app. PaaS (Heroku, App Engine, Render): you deploy code, provider manages OS and runtime. SaaS (Gmail, Salesforce): fully managed application. FaaS (Lambda): function-level deployment, fully managed. The shared responsibility model defines what the cloud provider secures vs what you secure. As you move up the stack, you give up control but gain operational simplicity. PHP developers typically work at PaaS or IaaS level.

Diagram

flowchart TD
    subgraph You manage
        IAAS_YOU[OS, Runtime,<br/>App, Data]
        PAAS_YOU[App, Data]
        SAAS_YOU[Nothing]
    end
    subgraph Provider manages
        IAAS_P[Physical infra<br/>Hypervisor]
        PAAS_P[Physical + OS<br/>+ Runtime]
        SAAS_P[Everything]
    end
    IAAS[IaaS<br/>eg. EC2] --- IAAS_YOU & IAAS_P
    PAAS[PaaS<br/>eg. Heroku] --- PAAS_YOU & PAAS_P
    SAAS[SaaS<br/>eg. Gmail] --- SAAS_YOU & SAAS_P
    FAAS[FaaS / Serverless<br/>eg. Lambda] -.->|you write functions only| PAAS
style IAAS fill:#1f6feb,color:#fff
style PAAS fill:#238636,color:#fff
style SAAS fill:#6e40c9,color:#fff
style FAAS fill:#d29922,color:#fff

Common Misconception

Why It Matters

Common Mistakes

• Treating PaaS like IaaS — PaaS platforms have constraints (ephemeral filesystems, managed runtimes) that IaaS does not.
• Assuming SaaS vendors handle all security — the shared responsibility model means you are still responsible for data and access management.
• Not considering vendor lock-in at the PaaS layer — proprietary PaaS features make migration expensive.
• Underestimating the operational overhead of IaaS — 'just spin up a VM' requires patching, monitoring, backups, and security hardening.

Code Examples

# IaaS with no management — missing the operational burden:
terraform apply  # EC2 instance created
# Who patches it? Who monitors it? Who backs it up?
# Who responds when the disk fills? When the process crashes?
# IaaS requires answering all of these — PaaS handles them

# Right tool for the job:
# Simple web app → PaaS (Heroku, Render, Railway) — no ops overhead
# Need custom OS config → IaaS (EC2, GCE) — full control
# Event processing → FaaS (Lambda, Bref) — pay per use
# Email service → SaaS (SendGrid, Postmark) — not your core competency

References

• ↗ https://aws.amazon.com/types-of-cloud-computing/

Tags

Related Terms