Best Practices and Advanced Features

This final lesson covers DynamoDB's advanced features — Time to Live (TTL), DynamoDB Accelerator (DAX), Global Tables, and PartiQL — along with a comprehensive set of best practices for production workloads.

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Time to Live (TTL)

TTL automatically deletes expired items from a table at no cost (no WCU consumed):

How TTL Works

1. You designate an attribute as the TTL attribute (e.g., ExpiresAt)
2. The attribute value must be a Unix epoch timestamp (Number type)
3. DynamoDB periodically scans for items where the TTL value is in the past
4. Expired items are deleted (typically within 48 hours of expiration)
5. Deletions are recorded in DynamoDB Streams (as REMOVE events with userIdentity.type = "Service")

Enabling TTL

aws dynamodb update-time-to-live \
  --table-name Sessions \
  --time-to-live-specification \
    Enabled=true,AttributeName=ExpiresAt

Writing an Item with TTL

# Set expiry to 24 hours from now (Unix timestamp)
aws dynamodb put-item \
  --table-name Sessions \
  --item '{
    "SessionId": {"S": "sess-abc123"},
    "UserId": {"S": "user-001"},
    "ExpiresAt": {"N": "1709654400"}
  }'

Common TTL Use Cases