Block finality refers to the concept that a proposed block is finalized by the blockchain and can not be reverted or the cost of reversion is prohibitively high. Block finality is usually measured by how long it takes for the newly proposed blocks to be finalized. For example, in Ethereum, it takes more than 6 blocks or 1 minute to have reasonable confidence that the block is finalized and can not be reverted.
Thanks to the nature of Harmony‘s FBFT consensus, blocks can be finalized as long as the 2/3 majority quorum is reached on the block. On Harmony mainnet, it now takes 2 seconds to finalize a newly proposed block and the transactions inside. Read more about our 2-second finality here:
Harmony follows the same transaction fee model as Ethereum where users pay a certain amount of tokens to get their transactions processed and included in the blockchain. Since Harmony is fully EVM-compatible, users can translate directly the fee model from Ethereum and apply to Harmony. For example, a normal token transfer transaction cost 21000 gas. The gas price can be as low as 0.000000001 ONE (or 10 Gwei as in Ether) since Harmony have high TPS and the network is highly efficient and rarely clogged. This means a normal transfer cost only about 0.000021 ONE. In General, transactions in Harmony network cost around $0.000001 gas fee.
The reason for Harmony to be able to afford such low fee is twofold. First, Harmony is Proof-of-Stake chain where the cost of running a node is much cheaper than PoW chains as no wasteful computation is needed. Second, Harmony is a highly scalable blockchain which currently provide thousands of transactions per seconds as throughput. This means users don't need to bid with high fee to get their transaction processed in time. We expect the low fee situation will stay as long as Harmony network is not fully utilized and even if that happens, we can solve the problem by extending the network with more shards to provide more transaction processing power.