The primary duty of Peerplays Witnesses is to bundle transactions into blocks and sign them with their signing key, and they are rewarded with PPY tokens for each block they validate in this way. Witnesses keep the blockchain alive by producing one block every three seconds. For example, if there were 20 Witnesses, each would produce 1 block in every 60 second period.
Witnesses must operate a full node with enough bandwidth to support current network activities. Many Witnesses also choose to operate API nodes to support end user applications.
Witnesses also have the authority to integrate (or reject) any changes to the blockchain software that are published. Forking consensus is maintained through stakeholder voting, because PPY Token holders can remove their votes from any Witness with whom they do not agree. To ensure that no untested or harmful code enters the blockchain, many Peerplays Witnesses have also chosen to operate a test version of the Peerplays blockchain that functions as a public testing environment.
The job of Peerplays Witness is a paid position, but there aren’t any job interviews or resumés. Instead, to become a Witness you need to convince the Peerplays community (PPY token holders) to vote for you. This is often achieved by Witnesses posting information about how they intend to perform their duties as a Witness, and other ways in which they bring value to Peerplays, for example helping to maintain the Public Test Net. For more details on Witness lobbying, please check out ‘Witness URLs’ on the Peerplays Block Explorer.
Bookie, the decentralized sports betting exchange app for the Peerplays blockchain, requires that Peerplays Witnesses also act as decentralized oracles, which means that the Witnesses are required to populate the Peerplays blockchain with real-world sporting data. For example, league and competition data, event data, betting market data for different sports (soccer, basketball, football, tennis, etc.), along with the final scores of each game. Smart contracts then use this data to grade and settle bets placed by users on Bookie.