> ## Documentation Index
> Fetch the complete documentation index at: https://upstash-fix-issues-on-docs.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Use Serverless Kafka to Produce Events in AWS Lambda

In this tutorial, we will produce events to Upstash Kafka from an AWS Lambda
function.

### Create Kafka

First, create an Upstash Kafka cluster and topic following
[those steps.](../overall/getstarted) You will need the endpoint, username and
password in the following steps.

<Frame>
  <img src="https://mintlify.s3-us-west-1.amazonaws.com/upstash-fix-issues-on-docs/img/kafka/howto/awslambda/cluster_detail.png" width="100%" />
</Frame>

### Create Project

We will use Serverless Framework to create the application.

```shell
kafka-examples git:(master) serverless
 What do you want to make? AWS - Node.js - HTTP API
 What do you want to call this project? produce-in-lambda
Downloading "aws-node-http-api" template...
Project successfully created in produce-in-lambda folder
```

Then we will initialize a node project and install axios dependency.

```shell
npm init
npm install axios
```

### Implement the Lambda Function

Open the handler.js and update as below:

```javascript
const fetch = require("axios").default;

module.exports.hello = async (event) => {
  const msg = "Hello";
  const address = "https://REPLACE_YOUR_ENDPOINT";
  const user = "REPLACE YOUR USERNAME";
  const pass = "REPLACE YOUR PASSWORD";
  const auth = Buffer.from(`${user}:${pass}`).toString("base64");
  const response = await fetch(`${address}/produce/newtopic/${msg}}`, {
    headers: {
      Authorization: `Basic ${auth}`,
    },
  });
  const res = response.data;

  return {
    statusCode: 200,
    body: JSON.stringify(
      {
        header: "Pushed this message to Upstash Kafka with REST API!",
        message: msg,
        response: res,
      },
      null,
      2
    ),
  };
};
```

You need to replace the endpoint, username and password above with the values
that you copy from the [Upstash Console](https://console.upstash.com).

The above code simply creates a producer and sends the message to Kafka.

### Deploy the Lambda Function

You can deploy your function to AWS by running:

```
serverless deploy
```

This command will output your URL. The output should be something like this:

```json
{
  "header": "Pushed this message to Upstash Kafka!",
  "message": {
    "value": "Hello message"
  }
}
```

### Test the Function

Now let’s validate that the messages are pushed to Kafka. We can consume the
Kafka topic using the REST API. You can copy the curl code to consume from the
Upstash Console.

```
produce-in-lambda git:(master) ✗ curl https://full-mantis-14289-us1-rest-kafka.upstash.io/consume/GROUP_NAME/GROUP_INSTANCE_NAME/newtopic -u REPLACE_USER_NAME:REPLACE_PASSWORD

[ {
  "topic" : "newtopic",
  "partition" : 0,
  "offset" : 98,
  "timestamp" : 1639610767445,
  "key" : "",
  "value" : "Hello message",
  "headers" : [ ]
} ]%
```

### REST vs Kafka Client

We can also use a native Kafka client (e.g. KafkaJS) to access our Kafka
cluster. See
[the repo](https://github.com/upstash/kafka-examples/tree/master/produce-in-lambda)
for both examples. But there is a latency overhead if connecting (and
disconnecting) to the Kafka with each function invocation. In our tests, the
latency of the function with REST is about 10ms whereas it goes up to 50ms when
KafkaJS is used. Kafka client's performance could be improved by caching the
client outside the function but it can cause other problems as explained
[here](https://blog.upstash.com/serverless-database-connections).

**Troubleshooting:** If Lambda function outputs `internal error`, check the
cloudwatch log **(Lambda > Monitor > View logs in CloudWatch)**.