Stop Using Lambda on Everything: EC2 Is Better Than Lambda In These Cases. Lambda is effective, yet it is not a solution to all the backend issues. The following is a viable decision model to select EC2 over Lambda.
Introduction
Such a default instance is commonly sold as Lambda on AWS. And that's the problem.
We, as software engineers, have added to making workloads push into Lambda, which is working against us. This is not a post against serverless. It's anti-blind serverless.
I will discuss the reasons why Lambda is not the correct tool, the reasons why EC2 remains useful, and why this is not dogmatic in making this choice.
Why Lambda Became the Default (And Why That is Dangerous).
- Zero server management
- Pay-per-use pricing
- Close integration of AWS ecosystem.
- Heats himself up (sometimes)
However, there are dangerous cases when there is no context.
Beyond Pricing The Hidden Costs of Lambda.
1. Cold-Starts-a-Design-Limit.
- VPC cold starts
- Differences in language runtime.
- The reason why provisioned concurrency is not free.
2. There is a Limit to Execution that defines Your Architecture.
- 15-minute timeout
- Memory ≠ CPU in intuitive ways
- No long-lived connections
3. How to debug the code in the production is worse than you think.
- Distributed logs
- Async retries
- Semi failures are the order of the day.
Where EC2 Makes More Sense (Yes, Indeed)
Long-Running/Stateful Processes.
Examples:
- WebSocket servers
- Queue workers
- Video processing
- ML inference services
Foreseeable Traffic Flow.
If traffic is steady:
- Lambda loses pricing advantage.
- EC2 is made easy and cheaper.
Memory or Heavy CPU Workloads.
- Lambda pricing rewards resource parsimony.
- Instances classes are under your complete control with EC2.
Comparison of the Real Costs of Lambda vs EC2.
Numbers don't lie -- feelings do.
(Include:
- Monthly Lambda cost example
- EC2 t4g / t3 comparison
- Break-even analysis)
Operational Reality: EC2 Is No Longer Hard.
Modern EC2 ≠ 2015 EC2.
- Auto Scaling Groups
- Launch Templates
- ALB health checks
- CloudWatch + SSM
This is not "pet servers." This is cattle done right.
My Decision Framework (Use This, Not Hype)
Ask these questions:
- Does this workload have to last beyond 5-10 minutes?
- Is traffic predictable?
- Am I required to have constant contacts?
- Is acceptable cold start latency?
- Does it really increase operational simplicity?
Lambda will punish you in case you answer wrong questions.
Hybrid Architectures Win
The actual solution is neither Lambda nor EC2.
It's:
- Lambda for glue code
- EC2 for core workloads
- Where it makes sense event-driven.
Final Take
Scalpel, not hammer.
When all your system is made out of Lambdas you are not actually building serverless systems--you are just evading a decision.
Make the decision. Own the tradeoffs