AWS EC2 — Elastic Compute Cloud
Before you start: basic AWS familiarity (Regions, AZs, IAM roles) is assumed — see the AWS Core Services Overview and IAM courses first if those are new. No prior virtual-machine administration experience is needed.
EC2 is the backbone of AWS compute. It gives you virtual machines (instances) in the cloud that you can provision in minutes, scale automatically, and pay for only what you use.
What is EC2?
Amazon EC2 (Elastic Compute Cloud) provides resizable compute capacity in the cloud. An EC2 instance is essentially a virtual machine running on AWS infrastructure, but with cloud-native superpowers: auto-scaling, spot pricing, placement groups, elastic IPs, and deep integration with every other AWS service.
Instance Types
EC2 has hundreds of instance types organized into families (needs verification — exact current count grows regularly as AWS releases new generations):
| Family | Optimized For | Example | Use Case |
|---|
|--------|--------------|---------|----------|
| **t3/t4g** | General (burstable) | t3.medium | Dev/test, small web apps |
|---|---|---|---|
| m6i/m7i | General balanced | m6i.xlarge | Web servers, app servers |
| c6i/c7i | Compute | c6i.2xlarge | CI/CD, batch, web frontends |
| r6i/r7i | Memory | r6i.4xlarge | Databases, in-memory cache |
| i3/i4i | Storage (NVMe) | i3.xlarge | High I/O databases |
| p3/p4d | GPU | p3.2xlarge | ML training, graphics |
| g4dn/g5 | GPU (inference) | g4dn.xlarge | ML inference, video |
Naming convention: c6i.2xlarge
c = compute optimized family
6 = 6th generation
i = Intel processor (a = AMD, g = Graviton/ARM)
2xlarge = size (8 vCPU, 16 GB RAM)
EC2 Pricing Models
| Model | Savings vs On-Demand | Commitment | Best For |
|---|
|-------|---------------------|------------|----------|
| **On-Demand** | 0% (baseline) | None | Unpredictable, short-term |
|---|---|---|---|
| Reserved (1yr) | ~40% | 1 year | Steady-state workloads |
| Reserved (3yr) | ~60% | 3 years | Long-term stable workloads |
| Savings Plans | ~40-60% | 1 or 3 years | Flexible (compute or EC2) |
| Spot | ~70-90% | None (interruptible) | Batch jobs, stateless apps |
| Dedicated Host | — (premium) | On-demand or reserved | Licensing, compliance |
💡 FinOps tip: Use Reserved Instances or Savings Plans for your baseline, Spot for burst/batch. Never run all On-Demand in production.
Core Concepts
AMI (Amazon Machine Image) — Template containing OS, pre-installed software, and configuration. AWS provides official AMIs (Amazon Linux 2023, Ubuntu, Windows Server). You can create custom AMIs from running instances.
Security Groups — Stateful virtual firewall at the instance level. Rules are allow-only (no explicit deny). Inbound and outbound rules control traffic. Changes apply immediately.
Key Pairs — SSH public/private key pair for Linux instance access. AWS stores the public key, you keep the private (.pem) file. If you lose it, you can't SSH in.
Elastic IP — Static IPv4 address for your account. Instances get public IPs by default but they change on stop/start. Elastic IPs persist. Free when attached to running instance, charged when unattached.
User Data — Shell script or cloud-init that runs once when instance first boots. Use it to install packages, configure the instance, download code.