We’ll look at the security risks inherent in using off-chain systems e.g. data feeds to trigger your smart contracts, and how these security risks can be minimized using a combination of decentralization and trusted execution environments. We’ll cover the failure scenarios to be avoided when smart contract’s rely on off-chain systems via an oracle mechanism as their trigger and/or payment mechanism. Closely examining the key concepts and practical methods that smart contract developers should keep in mind for minimizing avoiding the most common failure scenarios when connecting their smart contract to external systems for data/off-chain events, web APIs and/or off-chain payments.