What is Serverless? An Introduction to AWS Lambda

One of the most transformative trends in cloud computing over the past few years has been the rise of serverless architecture. But the name "serverless" can be a bit misleading. It doesn't mean there are no servers; it just means that you, the developer, no longer have to think about them.

Serverless is an operational model where the cloud provider (like AWS) is responsible for managing the server infrastructure for you. You just write and deploy your code, and the cloud provider automatically handles the provisioning, scaling, and maintenance of the servers needed to run it.

The service that pioneered this model and remains at the heart of the serverless movement is AWS Lambda.

What is AWS Lambda?

AWS Lambda is a Function-as-a-Service (FaaS) platform. It's a compute service that lets you run code without provisioning or managing servers. With Lambda, you package your code into functions and upload them to the service. Lambda then executes your function only when it's needed and scales automatically, from a few requests per day to thousands per second.

How Does Lambda Work?

1. Event-Driven: Lambda functions are designed to be triggered by events. An event can be almost anything in your AWS environment:

   • An HTTP request from Amazon API Gateway.
   • A new file being uploaded to an S3 bucket.
   • A new message in an SQS queue.
   • A change to an item in a DynamoDB table.
   • A scheduled event (like a cron job).

2. Write a Function: You write your code in one of the supported languages (like Python, Node.js, C#, or Go). The function takes the event data as input, performs some logic, and can return a result.

3. Pay-per-Execution: This is a key benefit of serverless. You pay only for the compute time you consume. You are charged based on the number of requests for your functions and the duration (in milliseconds) it takes for your code to execute. If your code isn't running, you're not paying for anything.

A Simple Example: Image Thumbnailing

Let's consider a classic serverless use case: creating a thumbnail every time a new image is uploaded to your application.

The Old Way (with servers): You would need a server that is constantly running, waiting for new images to be uploaded. You would have to manage this server, patch it, and make sure it's always available. You'd be paying for it 24/7, even if no images are being uploaded.

The Lambda Way (serverless):

1. You create an S3 bucket for your images.
2. You write a Lambda function that takes an S3 event as input, reads the newly uploaded image, resizes it, and saves the thumbnail to another S3 bucket.
3. You configure the S3 bucket to trigger your Lambda function whenever a new object is created.

Now, your thumbnail generation code only runs when an image is actually uploaded. It scales automatically if 1,000 images are uploaded at once, and you pay absolutely nothing when it's idle.

The Benefits of Serverless

• No Server Management: This is the biggest advantage. You can focus on your application's code, not on managing and operating servers.
• Automatic Scaling: Lambda automatically scales your application by running code in response to each trigger. Your function runs in parallel and processes each trigger individually.
• Reduced Cost: The pay-per-value model can be extremely cost-effective for applications with variable or infrequent traffic.
• Increased Agility: Serverless allows you to build and ship applications faster, as you don't have to worry about infrastructure provisioning.

Limitations and Considerations

Serverless is not a silver bullet. There are some limitations to be aware of:

• Execution Time: Lambda functions have a maximum execution time (which was 15 minutes in 2019). They are not suitable for very long-running processes.
• Cold Starts: The first time a function is invoked after a period of inactivity, there can be a small amount of latency as Lambda provisions a new execution environment. This is known as a "cold start."
• Statelessness: Lambda functions are stateless. You cannot store any data in the execution environment between invocations. Any state must be stored in an external service like DynamoDB or S3.

Conclusion

Serverless computing with AWS Lambda represents a fundamental shift in how we build and deploy applications in the cloud. By abstracting away the underlying infrastructure, it allows developers to focus on delivering business value and building highly scalable, cost-effective applications with unprecedented speed. For a huge range of use cases, serverless is not just a viable option; it's the best option.