You can access the Stream API automatically using a Live Application Key.
For access to the Stream API using a Delayed App Key please contact Developer Support
Stream API data will be conflated when returned using the Delayed App Key. This means that you will receive any changes that have occurred in the last 3 minutes in a single message every 3 minutes.
If you wish to consume live Stream API data for trading purposes you'll require a Live Application Key. To apply for a Live Application key please click here and select Exchange API > For My Personal Betting and complete the application form at the bottom of the page. A one-off activation fee of £299 applies; this is debited directly from your Betfair account once access is approved.