Serverless Made Simple: Why Lambda Is Changing the Future of Cloud

What is Serverless?

Serverless does NOT mean “there are no servers.
It means...
You don't manage the servers. AWS manages everything for you.

You only write code, and AWS handles:

• servers
• scaling
• uptime
• patches
• networking
• infrastructure

You pay only when your code runs.

Let's understand with example...

Imagine you want to run a function.
Instead of buying a computer, you ask AWS:
‘Please run this code whenever needed.’
AWS does the rest.

Why Serverless Exists?

Before serverless:

• you must choose server size
• you must keep it running
• you must pay 24/7
• you must scale manually
• you must monitor and reboot

With serverless:

• no servers to manage
• no scaling worries
• no idle costs
• automatically handles millions of users
• ideal for APIs, cron jobs, triggers

What is AWS Lambda?

AWS Lambda is THE most famous serverless service.

Lambda = run your code without servers.

You upload your code → AWS executes it when needed → you pay only for milliseconds used.

How Lambda works???

                     Event Occurs
                           |
                  Lambda (Runs Code)
                           |
                        Output

Examples of events that trigger Lambda:

• API call from API Gateway
• File uploaded to S3
• DynamoDB table change
• SNS message
• SQS queue message
• CloudWatch cron job
• IoT event

Let's understand how Lambda executes code internally!

• Firstly, any event happens. Like user hits button or login API.
• Lambda who was sleeping,wakes up!
• User code executes.
• Lambda return results or writes to database.
• Lambda goes for sleep again!(shuts down..no server stays running)

Cold Start vs Warm Start (Important)

When a Lambda function runs, AWS needs to prepare an execution environment for it.
This environment includes:

• CPU + memory allocation
• Runtime setup (Node/Python/Java…)
• Your code loading
• Dependencies loading (npm, libs, etc.)
• Environment variables
• Network setup (VPC ENI if used)

Depending on whether this environment already exists or not, Lambda behaves differently.

COLD START

A cold start happens when:

• It’s the first time Lambda is running
• Lambda hasn’t been used for some time
• Lambda is deployed new version
• AWS scaled up and needed new containers
• You changed VPC settings (most costly cold starts)

Because Lambda doesn’t keep containers alive forever.
It sleeps after inactivity to save cost.

Also when traffic spikes:

If suddenly 1000 users come at once → AWS creates 1000 fresh containers → cold starts for many.

WARM START

A warm start happens when AWS already has a prepared container for your Lambda.

Meaning:

• Lambda ran recently
• AWS kept the container alive (in warm pool)
• No setup needed
• Code executes instantly

AWS keeps Lambda containers warm for some minutes (usually 5–15 minutes), hoping the function will be used again.

Understand with a simple story...

Warm Start - Suppose a gas stove is already hot and you can cook immediately.
Cold Start - Suppose a gas stove is cold and you must light it,heat it and then start cooking.

Lambda vs EC2

Feature	Lambda	EC2
Server Management	None	You manage
Pricing	Pay per execution	Pay per hour
Scaling	Automatic	Manual/Auto scaling
Ideal For	Small bursts, events	Heavy apps, long-running apps
Always running?	No	Yes
Cold start	Yes	No
Control Level	Low	High
OS access	No	Yes

When to Use Lambda?

Use Lambda when:

• You need API endpoints.
• You want event-driven apps.
• You only need code to run occasionally.
• You want low cost.
• You want no server maintenance.

When NOT to Use Lambda?

Use EC2 instead if:

• You need app running 24/7
• You have heavy CPU tasks
• You need custom OS configurations
• You want to host databases or big backend apps
• You need persistent connections (sockets, games, chat servers)

What is the Serverless Framework?

The Serverless Framework is a tool used to create and deploy serverless apps easily.So, instead of:

• creating Lambda manually
• adding triggers manually
• connecting API Gateway manually
• configuring permissions manually

❗ Serverless Framework does everything for you.

File syntax is something like this:

service: my-service
provider:
  name: aws
  runtime: nodejs18.x

functions:
  hello:
    handler: handler.hello
    events:
      - http:
          path: hello
          method: get

Then, we run below command on terminal:

serverless deploy

And boom 💥
It creates:

• Lambda
• API Gateway routes
• Permissions (IAM roles)
• Logs (CloudWatch)
• And deploys everything

Serverless Framework = DevOps Shortcut

It automates:

• Packaging code
• Creating CloudFormation
• Deploying Lambda
• Creating APIs
• Versioning
• Permissions
• Environment variables
• Stages (dev, prod, test)

Very popular in companies for serverless architectures.

Let's see complete architecture!