Finality Is a Spectrum

People talk about finality like it's binary. Transaction is final or it isn't. Reality is messier. There are degrees of finality with different guarantees and timelines.

Probabilistic finality is what Bitcoin has. Each new block makes reversal exponentially harder. After six blocks, reversal is impractical. But never mathematically impossible. Good enough for most purposes.

Economic finality comes from proof of stake. Reverting finalized blocks requires mass slashing. Attackers lose their stake. The finality is as strong as the economic cost to break it.

Cryptographic finality is what ZK rollups provide eventually. Once the proof is verified on L1 and enough time passes, the state is as final as Ethereum itself. Mathematical certainty inherited from the base layer.

Fast finality versus strong finality is the tradeoff. Preconfirmations give you speed. L1 settlement gives you strength. Applications should pick based on their risk tolerance.

I think about finality requirements explicitly now. How much is at stake? How fast do I need confirmation? What's the cost of reversal? Match the finality guarantee to the use case.