🚀 Cloud Virtual Machines vs. Serverless Functions: What Should You Use?

When building modern applications in the cloud, choosing the right compute model can make or break your architecture. Should you go with Virtual Machines (VMs) like AWS EC2 or GCP Compute Engine? Or embrace the speed and simplicity of Serverless Functions like AWS Lambda or Google Cloud Functions?

Let’s break it down!

☁️ What Are Cloud Virtual Machines?

Cloud Virtual Machines are virtualized servers in the cloud that mimic traditional on-premise hardware. Instead of buying them (like car purchase), you rent them (like car leasing).

You get full control over the operating system, installed software, network configuration, and more.

Think of them as your own remote computer in a data center.

Popular services:

• AWS EC2

• Google Compute Engine

• Azure Virtual Machines

✅ Advantages of Virtual Machines:

• Full control over the environment (OS, libraries, runtimes)

• Persistent storage and IP addresses

• Long-running processes are supported (e.g., background jobs)

• Ideal for legacy apps or systems that can’t be refactored

• Can run any workload - from web servers to game engines

❌ Disadvantages:

• More DevOps overhead: you handle updates, security patches, and scaling

• Slow startup time (minutes vs. milliseconds)

• You pay for uptime 💰, even if the app is idle

• Less cost-efficient for sporadic or bursty workloads

⚡️ What Are Serverless Functions?

Serverless Functions (also known as Functions-as-a-Service or FaaS) abstract away the server entirely. You simply write a function that responds to events - HTTP requests, database changes, file uploads, etc.

Popular services:

• AWS Lambda

• Google Cloud Functions

• Azure Functions

✅ Advantages of Serverless Functions:

• No server management // deploy code, and you're done

• Automatic scaling // from zero to millions of requests

• Pay-as-you-go // you’re charged only when the function runs

• Fast deployment and easier for small, focused services

• Great for event-driven architectures and microservices

❌ Disadvantages:

• Limited execution time (e.g., max 15 minutes per invocation)

• Stateless // you can’t store data in-memory between runs

• Cold starts // some delay when scaling from zero

• Harder to debug with no direct access to the OS or file system

• Not suitable for heavy, persistent workloads

📊 TL;DR Table

Feature	Virtual Machines	Serverless Functions
Infrastructure	You manage it	Fully abstracted
Startup Time	Minutes	Milliseconds–seconds
Runtime	Unlimited	Time-limited
State	Can be stateful	Stateless
Scaling	Manual or configured	Automatic
Cost	Pay per uptime	Pay per execution
Use Case	General-purpose workloads	Event-driven, short-lived functions

🤔 When Should You Use Each?

Your Scenario	Choose
You’re running a web server 24/7	VM
You need full OS control (e.g., custom drivers)	VM
You’re processing file uploads or running short scripts	Serverless
You’re building APIs or microservices	Serverless
You’re migrating a legacy app	VM
You want to scale quickly with minimal effort	Serverless
Your app needs to maintain local state	VM

Those will indicate whether you should use VM or Serverless. But in order to be more precise, one should predict the many factors to make the right decision:

1. Estimated traffic // Is it high, low, or highly variable?

2. Response rate // How fast must the system respond under load?

3. Startup time tolerance // Can you afford cold starts (common in serverless)?

4. Execution duration // Are tasks short-lived or long-running?

5. and more...

TL;DR:

If you’re building a long-running, complex application - go with VMs. If you want to move fast and focus purely on business logic - go serverless.

🧠 Hybrid Architectures

You don’t always have to choose one over the other. Many modern applications use a hybrid approach:

• Run your main app on a VM or container (Cloud Run, Kubernetes)

• Use serverless functions for async tasks, triggers, or APIs

This lets you balance control, performance, and cost-efficiency.

👩‍💻 Let’s Wrap It Up

Both Virtual Machines and Serverless Functions are powerful in their own right. The best choice depends on your workload, scalability needs, and how much infrastructure you want to manage.

Want help deciding which fits your next project? DM me or drop a comment - happy to help & Shabbat Shalom! 💬

🍋 The Hackerista