EC2 vs Lambda

Amazon EC2 and AWS Lambda represent two fundamentally different compute paradigms. EC2 gives you full virtual machines with complete control. Lambda gives you serverless functions that scale automatically with zero server management. Most modern architectures use both.

The Fundamental Tradeoff

EC2 trades operational overhead for control and flexibility. You choose the OS, install software, configure networking, and manage patches. In return, you get unlimited runtime, any resource configuration, and predictable performance without cold starts.

Lambda trades control for operational simplicity. You write a function handler, and AWS manages everything: provisioning, scaling, patching, and monitoring. In return, you accept execution limits (15 min), resource constraints (10 GB RAM), and cold starts.

Cost Analysis

For steady-state workloads running 24/7, EC2 is significantly cheaper. A reserved t3.medium costs about $25/month. The equivalent compute on Lambda at sustained invocation would cost hundreds.

For bursty or low-traffic workloads, Lambda wins dramatically. If your function runs 100,000 times per month for 200ms each, it costs under $1. The equivalent EC2 instance sitting idle 99% of the time costs $25+/month.

Scaling Characteristics

Lambda scales from zero to thousands of concurrent executions in seconds. EC2 Auto Scaling Groups take minutes to launch new instances, though pre-warming and predictive scaling can help.

For traffic patterns that spike suddenly (viral content, flash sales, webhook bursts), Lambda's instant scaling is invaluable. For steady traffic with gradual growth, EC2's ASG scaling is sufficient and more cost-effective.

Common Architecture Pattern

Many production systems combine both: Lambda handles API Gateway requests, event processing, and automation. EC2 (or Fargate) runs long-lived services, databases, and background workers. Understanding when to use each is a key system design interview skill. Explore our concepts, interview questions, and pricing.