When you search for a transaction which is not yet mined and cannot be found in the system, Tenderly will retrieve said transaction directly from the node pending pool and Simulate it using the most recent state.
Simulated Pending Transaction - Failed
Simulated Pending Transaction - Successful
This means that you can see the expected outcome of your or any other transaction even before it is approved on the Mainnet.
This feature is available to all users and works by default whenever you search for a transaction which happens to be in the pending pool. You can also check out how to use the full power of our SimulationsandForks