In today's fast-paced world, building an efficient and scalable serverless application is becoming increasingly important for businesses looking to reduce costs, increase agility, and improve overall efficiency. While the process of building such an application can be complex, there are several key steps that you can follow to make it more manageable and effective.

Firstly, before diving into the details of building your serverless application, it's essential to understand what exactly it entails. A serverless application is one where you don't have to manage or monitor any infrastructure, making it highly scalable and flexible. It allows developers to focus on writing code rather than worrying about managing servers and other resources.

To build a serverless application using AWS Lambda, you'll need to first create a new Lambda function in the AWS Management Console. This will allow you to define your lambda functions and their triggers, which are events triggered when certain conditions are met.

Next, you'll need to define your lambda function's actions. These actions should be defined in your lambda function's code. For example, if you're building a simple web service, you might define a "GET" action with the following code:

```python

exports.handler = async (event) => {

console.log('Received event: ' + JSON.stringify(event));

return 'Hello World!';

};

```

This code defines a single event handler that logs the incoming event to the console and returns a response indicating that the request was received.

Once you've defined your lambda function, you'll need to configure it to run automatically whenever certain events occur. To do this, you'll need to add a trigger to your lambda function. You can use AWS CloudWatch Events to set up these triggers, or you can create a custom trigger.

Finally, you'll need to write your lambda function's code to handle the events triggered by your triggers. This involves defining your lambda function's logic and returning a response based on the results of those events. Here's an example of how you might structure your code:

```python

exports.handler = async (event) => {

try {

const { statusCode, body } = await someAction();

return {

statusCode,

body: JSON.stringify(body)

};

} catch (error) {

return {

statusCode: 500,

body: error.message

};

}

};

```

Note that while the above code snippet is just an example, it's designed to demonstrate how you might structure your lambda function's code. In practice, you may want to consider adding additional functionality, such as logging, authentication, or error handling, depending on the specific requirements of your serverless application.

Overall, building an efficient and scalable serverless application using AWS Lambda requires careful planning and attention to detail. By following these key steps and leveraging the benefits of cloud-native services like AWS, you can take advantage of the powerful features and flexibility offered by serverless applications.