A new DynamoDB application has long quiet periods and unpredictable bursts. The team cannot confidently forecast read or write demand and wants request-based billing without selecting provisioned capacity units in advance. Which capacity mode best fits this requirement?

1. Provisioned capacity permanently set to the highest conceivable burst rate.
2. DynamoDB on-demand capacity mode, with monitoring and consideration of applicable scaling behavior and quotas.
3. Provisioned capacity permanently set to one unit with no scaling or throttling plan.
4. Use provisioned capacity with auto scaling and select minimum and maximum capacity bounds before launch.