Time In Force orders expire after a set amount of seconds. This provides security and confidence to market makers that stale or miss-priced orders will not get left on the order book in event of network degradation or any other issue.
"placePerpOrder2" accepts an "expiryTimestamp" input which cancels an order after "n" seconds if it has not been executed.
Time In Force orders are available in client, Mango Bowl, Python Explorer, and REST/WebSocket APIs. More information on these services is in Developer Resources.