THERE IS AN AWS OFFICIALY SUPPORTED METHOD FOR DOING THIS!

As all good ideas in AWS, eventually their platform expands to include it: https://aws.amazon.com/blogs/aws/new-auto-scaling-for-amazon-dynamodb/. This project may issue critical bug fixes, but should be considered deprecated.

Prerequisites

Install Serverless framework globally:

$ npm install -g serverless

Deployment

Install node modules and deploy serverless stack to AWS account

$ npm install
$ sls deploy --stage <stage name>

Stage flag is optional...

Auto-Scale Lambdas

Auto-scaling lambdas are deployed with scheduled events which run every 1 minute for scale up and every 6 hours for scale down by default. Schedule settings can be adjusted in serverless.yml file.

Add an API Key

By default we protect all API endpoints, and the quickest way to get started is just API Gateway API Keys. Create a key, give it permissions to hit your stage. You leverage the key by passing it in with the x-api-key header on any requests to the Configuration REST API.

Configuration REST API

API gateway endpoints will be deployed to maintain auto-scaling configuration:

GET https://api.domain.name/ddb-auto-scale/config - Load all available configuration records.

GET https://api.domain.name/ddb-auto-scale/config/{tableName} - Load configuration record for specified DynamoDB table.

POST https://api.domain.name/ddb-auto-scale/config - Save configuration record for DynamoDB table (see Configuration Data Structure section below).

DELETE https://api.domain.name/ddb-auto-scale/config/{tableName} - Delete configuration record for specified DynamoDB table.

Configuration Data Structure

All auto-scaling properties for specified DynamoDB table along with its global secondary indexes are described by configuration JSON object with following structure:

{
	tableName: name of DDB table to auto-scale (required)

	min: minimal capacity units (default 1)
	max: maximal capacity units (default 100)
	
	threshold: value which determines if we need to scale (scale up if consummed capacity units >= provisioned capacity units * threshold, default 0.8)
	increase: number of capacity units by which we increase (default 10)
	 
	upTimeSpan: a time span for which we analyze consummed capacity units for scale up (default to 5 minutes)
	downTimeSpan: a time span for which we analyze consummed capacity units for scale down (default to 30 minutes)
	
	indexes: array of indexes scale configuration [
		indexName: an index name to auto-scale (required)
		
		... similar configuration structure as for table ...
	]
}