Choosing the wrong EC2 instance type means all subsequent optimizations are just patching leaks. This page provides a decision-making framework for selection, not a configuration recommendation table — because recommendations without specific use cases are meaningless.
Answer These Three Questions First
- What are you running?
Static websites, WordPress, Java applications, Python services, data processing tasks, and machine learning inference — different workloads have completely different requirements for CPU, memory, and IOPS.
- What is the concurrency level, and how stable does it need to be?
Daily traffic and peak QPS determine how many instances you need and their size; whether you can tolerate a few minutes of downtime determines if Auto Scaling is necessary.
- Which billing model do you want?
Reserved Instances or Savings Plans are most cost-effective for long-term stable workloads; On-Demand is suitable for fluctuating traffic; Spot Instances are ideal for interruptible batch processing. Choosing the wrong direction can lead to bill differences of several times.
Understanding Instance Families
| Family | Use Case | Notes |
|---|---|---|
| T / M | General Purpose: Web apps, databases, small-to-medium services | Average network performance; suitable for moderate traffic |
| C | Compute Optimized: High-concurrency web apps, application servers | The default choice for CPU-intensive tasks |
| R | Memory Optimized: Databases, caching, big data components | High memory-to-network ratio; preferred choice for databases |
| I | Storage Optimized: High throughput, low-latency I/O | Suitable for databases sensitive to disk performance |
| G / Graviton | ARM Architecture: More power-efficient and cost-effective than equivalent x86 | Ensure your software and images have ARM versions |
| P / G | GPU Instances: Machine learning and graphics processing | High cost; typically used with On-Demand or Spot, not Reserved |
Choosing a Billing Model
| Model | Best For | Approximate Discount |
|---|---|---|
| On-Demand | Temporary tasks, test environments, non-interruptible workloads | Base price |
| Reserved Instances (RI) | Single instance families running long-term and stably | ~20–50% off |
| Savings Plans | Long-term workloads that may change instance families or regions | ~20–40% off; more flexible than RIs |
| Spot Instances | Interruptible batch processing, rendering, data processing | Largest discount, but instances can be reclaimed |
Frequently Asked Questions
Is the free tier sufficient?
The free tier is only suitable for testing and small-scale usage, and its validity period is 12 months for some new accounts. Do not build production businesses on the free tier — after expiration, bills and resources will be affected, and overages can occur unexpectedly.
What if I’m unsure about the right instance size?
Use CloudWatch metrics to decide, rather than guessing. Run instances with loads close to reality for a period, monitor actual CPU, memory, network, and disk usage, then decide whether to scale up or down. Most customers’ actual needs are lower than estimated — downsizing often saves more money than optimization efforts.
Do you offer help with instance selection?
This is included in our AWS Technical Support. We provide recommendations on instance types, billing models, cost estimates, and downsizing advice. We do not simply push larger instances.