AWS Compute Blog

Increasing real-time stream processing performance with Amazon Kinesis Data Streams enhanced fan-out and AWS Lambda

Live business data and real-time analytics are critical to informed decision-making and customer service. For example, streaming services like Netflix process billions of traffic flows each day to help you binge-watch your favorite shows. And consumer audio specialists like Sonos monitor a billion events per week to improve listener experiences. These data-savvy businesses collect and analyze massive amounts of real-time data every day.

Kinesis Data Streams overview

To help ingest real-time data or streaming data at large scales, AWS customers turn to Amazon Kinesis Data Streams. Kinesis Data Streams can continuously capture gigabytes of data per second from hundreds of thousands of sources. The data collected is available in milliseconds, enabling real-time analytics.

To provide this massively scalable throughput, Kinesis Data Streams relies on shards, which are units of throughput and represent a parallelism. One shard provides an ingest throughput of 1 MB/second or 1000 records/second. A shard also has an outbound throughput of 2 MB/sec. As you ingest more data, Kinesis Data Streams can add more shards. Customers often ingest thousands of shards in a single stream.

Enhanced fan-out

One of the main advantages of stream processing is that you can attach multiple unique applications, each consuming data from the same Kinesis data stream. For example, one application can aggregate the records in the data stream, batch them, and write the batch to S3 for long-term retention. Another application can enrich the records and write them into an Amazon DynamoDB table. At the same time, a third application can filter the stream and write a subset of the data into a different Kinesis data stream.

Before the adoption of enhanced fan-out technology, users consumed data from a Kinesis data stream with multiple AWS Lambda functions sharing the same 2 MB/second outbound throughput. Due to shared bandwidth constraints, no more than two or three functions could efficiently connect to the data stream at a time, as shown in the following diagram.

Default Method

To achieve greater outbound throughput across multiple applications, you could spread data ingestion across multiple data streams. So, a developer seeking to achieve 10 GB/second of outbound throughput to support five separate applications might resort to math like the following table:

Stream Shards Input Output
1 1 1000 records/second
or 1 MB/second
2 MB/second
2 2500 ea. 5,000,000 records/second
or 5000 MB/second
10,000 MB/second
or 10 GB/second

Due to the practical limitation of two to three applications per stream, you must have at least two streams to support five individual applications. You could attach three applications to the first stream and two applications to the second. However, diverting data into two separate streams adds complexity.

In August of 2018, Kinesis Data Streams announced a solution: support for enhanced fan-out and HTTP/2 for faster streaming. The enhanced fan-out method is an option that you can use for consuming Kinesis data streams at a higher capacity. The enhanced capacity enables you to achieve higher outbound throughput without having to provision more streams or shards in the same stream.

When using the enhanced fan-out option, first create a Kinesis data stream consumer. A consumer is an isolated connection to the stream that provides a 2 MB/second outbound throughput. A Kinesis data stream can support up to five consumers, providing a combined outbound throughput capacity of 10MB/second/shard. As the stream scales dynamically by adding shards, so does the amount of throughput scale through the consumers.

Consider again the requirement of 10 GB of output capacity—but rerun your math using enhanced fan-out.

Stream Shards Input Consumers Output
1 1 1000 records/second
or 1 MB/second
5 10 MB/second
1 1000 1,000,000 records
or 1,000 MB/second
5 10,000 MB/second
or 10 GB/second

Enhanced fan-out with Lambda functions

Just before re:Invent 2018, AWS Lambda announced support for enhanced fan-out and HTTP/2. Lambda functions can now be triggered using the enhanced fan-out pattern to reduce latency. These improvements increase the amount of real-time data that can be processed in serverless applications, as seen in the following diagram.

Enhanced Fan-Out Method

In addition to using the enhanced fan-out option, you can still attach Lambda functions to the stream using the GetRecords API, as before. You can attach up to five consumers with Lambda functions at 2 MB/second outbound throughput capacity and another two or three Lambda functions sharing a single 2 MB/second outbound throughput capacity. Thus, enhanced fan-out enables you to support up to eight Lambda functions, simultaneously.


The streaming technology in HTTP/2 increases the output ability of Kinesis data streams. In addition, it allows data delivery from producers to consumers in 70 milliseconds or better (a 65% improvement) in typical scenarios. These new features enable you to build faster, more reactive, highly parallel, and latency-sensitive applications on top of Kinesis Data Streams.

Comparing methods

To demonstrate the advantage of Kinesis Data Streams enhanced fan-out, I built an application with a single shard stream. It has three Lambda functions connected using the standard method and three Lambda functions connected using enhanced fan-out for consumers. I created roughly 76 KB of dummy data and inserted it into the stream at 1,000 records per second. After four seconds, I stopped the process, leaving a total of 4,000 records to be processed.

As seen in the following diagram, each of the enhanced fan-out functions processed the 4000 records in under 2 seconds, averaging at 1,852 MS each. Interestingly, the standard method got a jumpstart in the first function, processing 4,000 records in 1,732 MS. However, because of the shared resources, the other two functions took longer to process the data, at just over 2.5 seconds.

Comparison of Methods

By Kinesis Data Streams standards, 4000 records is a small dataset. But when processing millions of records in real time, the latency between standard and enhanced fan-out becomes much more significant.


When using Kinesis Data Streams, a company incurs an hourly cost of $0.015 per shard and a PUT fee of $0.014 per one million units. You can purchase enhanced fan-out for a consumer-shard per hour fee of $0.015 and $0.013 per GB data retrieval fee. These fees are for the us-east-1 Region only. To see a full list of prices, see Kinesis Data Streams pricing.

Show me the code

To demonstrate the use of Kinesis Data Streams enhanced fan-out with Lambda functions, I built a simple application. It ingests simulated IoT sensor data and stores it in an Amazon DynamoDB table as well as in an Amazon S3 bucket for later use. I could have conceivably done this in a single Lambda function. However, to keep things simple, I broke it into two separate functions.

Deploying the application

I built the Kinesis-Enhanced-Fan-Out-to-DDB-S3 application and made it available through the AWS Serverless Application Repository.

Deploy the application in your AWS account. The application is only available in the us-east-1 Region.

On the deployment status page, you can monitor the resources being deployed, including policies and capabilities.

Deployment Status

After all the resources deploy, you should see a green banner.

Exploring the application

Take a moment to examine the list of deployed resources. The two Lambda functions, DDBFunction and S3Function, receive data and write to DynamoDB and S3, respectively. Additionally, two roles have been created to allow the functions access to their respective targets.

There are also two consumers, DDBConsumer and S3Consumer, which provide isolated output at 2 MB/second throughput. Each consumer is connected to the KinesisStream stream and triggers the Lambda functions when data occurs.

Also, there is a DynamoDB table called DBRecords and an S3 bucket called S3Records.

Finally, there is a stream consumption app, as shown in the following diagram.

Application Example

Testing the application

Now that you have your application installed, test it by putting data into the Kinesis data stream.

There are several ways to do this. You can build your producer using the Kinesis Producer Library (KPL), or you could create an app that uses the AWS SDK to input data. However, there is an easier way that suits your purposes for this post: the Amazon Kinesis Data Generator. The easiest way to use this tool is to use the hosted generator and follow the setup instructions.

After you have the generator configured, you should have a custom URL to generate data for your Kinesis data stream. In your configuration steps, you created a username and password. Log in to the generator using those credentials.

When you are logged in, you can generate data for your stream test.

  1. For Region, choose us-east-1.
  2. For Stream/delivery stream, select your stream. It should start with serverlessrepo.
  3. For Records per second, keep the default value of 100.
  4. On the Template 1 tab, name the template Sensor1.
  5. Use the following template:
        "sensorId": {{random.number(50)}},
        "currentTemperature": {{random.number(
        "status": "{{random.arrayElement(
  6. Choose Send Data.
  7. After several seconds, choose Stop Sending Data.

At this point, if all went according to plan, you should see data in both your DynamoDB table and S3 bucket. Use the following steps to verify that your enhanced fan-out process worked.

  1. On the Lambda console, choose Applications.
  2. Select the application that starts with serverlessrepo-.
  3. Choose Resources, DDBFunction. This opens the DynamoDB console.
  4. Choose Items.

The following screenshot shows the first 100 items that your database absorbed from the DDBFunction attached to KinesisStream through DDBConsumer.

DynamoDB Records

Next, check your S3 bucket,

  1. On the Lambda console, choose Applications.
  2. Select the application that starts with serverlessrepo-.
  3. Choose Resources, S3Records. This opens the S3 console.

As in DynamoDB, you should now see the fake IoT sensor data stored in your S3 bucket for later use.

S3 Records

Now that the demonstration is working, I want to point out the benefits of what you have just done. By using the enhanced fan-out method, you have increased your performance in the following ways.

  1. HTTP/2 has decreased the time from data producers to consumers to <=70 MS, a 65% improvement.
  2. At the consumer level, each consumer has an isolated 2 MB/second outbound throughput speed. Because you are using two consumers, it works out to 2x the performance.


Using Lambda functions in concert with Kinesis Data Streams to collect and analyze massive amounts of data isn’t a new idea. However, the introduction of enhanced fan-out technology and HTTP/2 enables you to use more functions at the same time without losing throughput capacity.

If you only connect one or two Lambda functions to a data stream, then enhanced fan-out might not be a great fit. However, if you attach more than three Lambda functions to a stream for real-time manipulation and data routing, it makes sense to evaluate this option.

I hope this helps. Happy coding!