EC2 vs Lambda: what is the difference?
Amazon EC2 gives you full control over always-on virtual servers you manage, while AWS Lambda runs your code on demand as serverless functions with no servers to manage — the choice comes down to control and steady workloads versus event-driven, pay-per-use simplicity. Both are ways of running code on AWS, but they sit at opposite ends of how much of the underlying infrastructure you touch. This guide sets out what each actually is, the practical differences that decide between them, and why most real architectures end up using a mix rather than picking one exclusively.
What each one is, briefly
Amazon EC2 gives you a virtual server — you choose its size, install and configure whatever it needs to run, and it stays running until you stop it, whether or not it is doing anything at that moment. Our what is Amazon EC2 explainer covers the concept in depth.
AWS Lambda runs a piece of your code in response to an event — a request, a file upload, a schedule — without you provisioning or managing any server at all; it starts when needed and stops when the work is done. Our what is AWS Lambda explainer covers that concept separately.
The key differences
The practical distinctions that decide between them:
- Management and operations — with EC2 you patch, secure and maintain the operating system yourself (or via automation you build); with Lambda, AWS manages the underlying infrastructure entirely.
- Cost model — an EC2 instance is typically billed for the time it is running, whether idle or busy; Lambda is billed for actual execution, so an idle function costs nothing.
- Scaling — EC2 scaling (adding or removing instances) is something you configure and manage, usually via auto scaling groups; Lambda scales automatically per invocation, without you provisioning capacity in advance.
- Workload fit — EC2 suits long-running, steady or unpredictable-duration processes; Lambda suits short, event-driven tasks triggered by something happening.
- Execution limits — an EC2 instance can run indefinitely; a Lambda function is subject to a maximum execution time per invocation, so very long-running jobs are not a fit (check AWS’s current documentation for the specific limit).
When to choose EC2
Reach for EC2 when a workload is long-running, needs to stay available continuously, requires full control over the operating system and installed software, or has a fairly predictable, steady level of demand that makes always-on capacity efficient rather than wasteful.
When to choose Lambda
Reach for Lambda when work is short-lived and triggered by an event — a file landing in storage, an API request, a scheduled task — especially when demand is spiky or unpredictable and you would rather not manage servers, patch operating systems, or pay for idle capacity between events.
Not always either/or
Many real architectures use both: a steady core service running on EC2 alongside Lambda functions handling occasional background tasks, integrations or event processing around it. There is also middle ground between the two — serverless containers such as AWS Fargate remove server management the way Lambda does but suit longer-running, containerised workloads that do not fit Lambda’s execution-time model. Our fargate-vs-lambda and serverless-vs-containers explainers cover that middle ground in more depth.
Where this appears in certification study
Choosing between EC2 and Lambda for a given workload is a recurring theme in the AWS Certified Solutions Architect Associate and the AWS Certified Developer Associate, and the underlying compute concepts are introduced at a high level in the AWS Certified Cloud Practitioner. The exam-depth detail on configuring either service belongs in our /revision study material.
Original practice questions, timed mock exams and revision notes. No card, nothing to pay.