Network
Blocks are produced by a fixed, published set of validators rather than by open competition. Right now there is 1 validator; the set has been unchanged since genesis.
Validators take turns proposing the next block, one every 2 seconds. If the proposer does not deliver in time, the others move to a new round with the next validator. Over the last 1,000 blocks there were 0 round changes.
A block is final once at least 1 of 1 validators sign it (two-thirds, rounded up). Their signatures, called commit seals, are stored in the block itself, so anyone can check who agreed. Recent blocks carried 1.0 seals on average.
Once sealed, a block is not reversed: there are no competing chains to reorganize. A transaction with one confirmation is final.
With 1 validator, the network keeps producing blocks if up to 0 are offline or faulty. A single-validator network stops if that validator stops; adding validators raises this tolerance.