How can I confirm whether a Solana transaction was successful?

[BillInUK]

I asynchronously sent a Solana transaction and received a transaction ID (txId), but I want to know the final status of the transaction, including whether it was successful, failed to execute, or discarded.

[BillInUK]

If the transaction is successful, I can query the transaction using the transaction ID and then parse it to make a judgment. However, if the transaction is discarded, how can I accurately determine that?

[BillInUK]

May I confirm based on the slot of the block I referenced? For example, if the slot of the block I referenced is less than 30 slots behind the current one and I still can't find the transaction, should I consider the transaction as dropped?