Sei published the Giga whitepaper

And the chain is targeting sub-250ms finality.
Here is where every major chain stands on finality :
$SEI sub-250ms
$APT Instant
$SUI Instant
$NEAR 600ms
$ALGO Instant
$AVAX 2s
$SOL 12.8s
$ETH 12m 48s
$BTC 60 min
That number makes most of what the industry calls "fast" look like it belongs to a different decade of technology.
Before the data, here is what finality actually means.
When you execute a trade on-chain, your transaction is not truly settled the moment it appears confirmed.
Finality is the point where that transaction becomes mathematically irreversible, where no validator or network condition, and no edge case can roll it back.
Block time and finality are two completely different things, and most people confuse them.
Solana's block time is 405ms, but its actual finality sits at 12.8 seconds.
That gap matters enormously for traders running any kind of time-sensitive strategy.