After looking into Solana extremely in-depth, I am failing to understand how blocks can be added to the chain within 800ms (as said in the docs). This doesn’t seem possible because the time to get block approvals from a supermajority amount of validators seems like it would take way longer than that? I think that these blocks are already validated long before they are added to the chain but I don’t understand how that is possible and when that occurs within an Epoch?

Please let me know. Thanks!

2 Answers 2


The tldr of it is that the VDF is used as a proof of history mechanism. Assuming a particular validator, leader or not, has the same starting state and receives the same transactions as input, they would calculate the same future state and thus result in a blockhash that matches other nodes.

I think you're getting stuck on wondering how consensus is reached right away. The truth is that it is not reached until later. Small "micro" forks happen all the time due to network packets getting lost, so as soon as a validator notices this, it is in its best interest to adjust course and pick a fork with majority support that maximizes its own incentives.

Consensus is reached eventually and validators would get themselves into trouble if they voted on forks that are not supported by others on the network.

Anatoly provides a pretty good description of it here (link includes timestamp to consensus portion).


Imagine you have a puzzle that consists of 100 pieces. If you try to bring together 100 pieces, it might take maybe an hour.

But if I already order them, maybe put an order number on each of them and pass the pieces to you, it might take only a minute to solve it.

Proof of history determines the order of transactions and these transactions can be processed in parallel. In the puzzle example, since the place of each piece is already known, there can be other people who help you to finish the puzzle.

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