Enable TTL on a Dynamodb Table in an Amplify project

TTL Feature

DynamoDB TTL (Time to Live) is a feature provided by Amazon Web Services (AWS) for its DynamoDB database service. It allows you to define a time period after which items in a DynamoDB table will expire and be automatically deleted. This feature is particularly useful for managing data that has a finite lifespan.

How it works

1. Attribute for Expiry: You specify a TTL attribute from your DynamoDB table. This attribute must contain a timestamp that represents the expiration time for each item in the table.

2. Automatic Deletion: DynamoDB automatically deletes an item from the table at its expiration time specified in the TTL attribute . This deletion process is handled by DynamoDB itself, so you don't need to write any code to manage the deletion of expired items.

3. Efficient Cleanup: DynamoDB continuously scans the table for expired items and removes them in the background. This ensures that your table stays optimized and doesn't become cluttered with expired data.

 How to enable TTL on any Dynamodb table from AWS management console

1. Navigate to the AWS Management Console -> DynamoDB service -> Tables, find your table and open it.

2. Go to Additional Settings and find Time to Live setting.

        

     3.  Click on Turn on button.

     4. In TTL settings: TTL attribute name, enter the name of the attribute which has the expiration time.

     5. Click on Turn on TTL button. 

How to enable TTL on a Dynamodb table in AWS Amplify project

1. Add TTL attribute  to the Graphql schema

    Find your graphql schema which is located at amplify/backend/api/<your_api_name>/ as schema.graphql. In your dynamodb schema definition, add one more attribute with type int. If the name of the attribute is ttl (can be any name of your choice), then add:

ttl: Int     

2. Add Expiration Time to the TTL attribute

    Add TTL value to your TTL attribute for each attribute. For e.g., if we want to set TTL of 30 days, we can determine the TTL value in Python using:

        

    from datetime import datetime, timedelta

    

    current_time = datetime.utcnow()

# Calculate the TTL timestamp (30 days from now)

    ttl_duration = timedelta(days=30)

    ttl_timestamp = current_time + ttl_duration

    # Convert ttl_timestamp to Unix epoch time (seconds)

    ttl_timestamp_unix = int(ttl_timestamp.timestamp())

    print("TTL Timestamp:", ttl_timestamp_unix)

      

• We use datetime.utcnow() to get the current UTC time.
• We then add 30 days to the current time using timedelta(days=30) to calculate the TTL timestamp.
• Finally, we convert the TTL timestamp to Unix epoch time using timestamp() method and then to integer, which gives us the TTL timestamp value that can be used in DynamoDB.

3. Use override feature to enable TTL on the dynamodb table

               amplify override api    

Run the command above to override Amplify-generated Amazon API Gateway resources.

The command creates a new overrides.ts file under amplify/backend/api/<resource-name>/.

Apply all the overrides in the override(...) function. For example if we want to enable TTL on 2 dynamodb tables, namely, 'MyDynamodbTable' namely and 'MonthlyReport' namely and the attribute name is 'ttl'namely in both the tables, our overrides.ts file should look like this:

 

import { AmplifyApiGraphQlResourceStackTemplate, AmplifyProjectInfo } from '@aws-amplify/cli-extensibility-helper';

export function override(resources: AmplifyApiGraphQlResourceStackTemplate, amplifyProjectInfo: AmplifyProjectInfo) {

resources.models['MyDynamodbTable'].modelDDBTable.timeToLiveSpecification = {

attributeName: 'ttl',

enabled: true

};

resources.models['MonthlyReport'].modelDDBTable.timeToLiveSpecification = {

attributeName: 'ttl',

enabled: true

};

}