# Hybrid PBFT/Aurand Polkadot uses a hybrid PBFT / Aurand consensus mechanism that has two degrees of finality. This consensus mechanism allows for relatively low latency state transitions while mitigating certain attacks to the network. ![](https://3162634398-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LLG7gr0ydPNrSJQ43vf%2F-LQBK08ZY318Wj4K1451%2F-LQBKnP6Ig8nCwKiXcoz%2Fpolkadot-aurand.jpeg?alt=media\&token=1efc4f52-0fe8-4f50-b4c7-486176251eb5) The PBFT derivative provides absolute finality. Aurand, a derivative of Aura, provides fast, simple, and intermediate finality. Every so many blocks there is a PBFT check-point that guarantees finality, while the Aurand sets up the intermediary states of finality. With Aurand one randomly chosen validator may propose a block, which \*may be reverted\* (faster). They are punished (slashed) for proposing invalid blocks or for going offline. With PBFT > 2/3 of staked validators must sign-off to \*guarantee finality\* (slower). PBFT finality happens every \~30 seconds while Aurand blocks are proposed every \~4-5 seconds, potentially faster. POC-4 will introudce Aura v2, a progressive-consensus with milestone finalisation ([https://github.com/paritytech/polkadot/milestone/4 …](https://t.co/vX5a2Z0lL5)). [@**web3foundation**](https://twitter.com/web3foundation) researcher Alistair Stewart is working on this alongside Polkadot core devs [@**gavofyork**](https://twitter.com/gavofyork) and [@**rphmeier**](https://twitter.com/rphmeier). Become an expert on Polkadot's consensus mechanism (through POC-3) by watching [@**gavofyork**](https://twitter.com/gavofyork) present [@**ParityTech**](https://twitter.com/ParityTech)'s [#**Substrate**](https://twitter.com/hashtag/Substrate?src=hash) at Event Horizon, starting at minute 17:30. ### used in * Polkadot {% embed url="" %} source