Proof of Authority (PoA) is a consensus mechanism that uses pre-selected trusted validators to certify transactions and add them to the blockchain.

Because of its centralized nature computations can be done faster and more efficient when compared to Proof-of-Work (PoW) or Proof-of-Stake (PoS). However, it also means that the network is controlled by a group of validators that can be compromised, coerced, brought down, or collude together.

PoA is often used in private or consortium blockchains, and can be useful for DeFi applications where fast transaction times and the involved parities know and trust each other.