Ouroboros Praos: Slots, Epochs, Leader Selection

I want to know how the slots, epochs and leader selection work on decentralized version of Cardano. Praos talks about epochs being 24K deep. I have seen alternative information on this forum on epochs being 21.6K slots deep and epochs themselves lasting 5 days.

Can you point me to an authoritative source that describes what exactly will be implemented?

I have read this resource, which is a great way to start getting your head around how the protocol works. Kudos to the person who posted it on the forum!


24K is not a slot measure. It’s just a way to say: “imagine epoch being equally divided into 24 parts”. Original Ouroboros, for example, talks about epoch being 10K, but it’s not relevant to slots. It just means - whatever your length of epoch is in slots - divide it in 10 parts.

At the moment there are exactly 21600 slots in each epoch, which makes epoch to be 5 days at 20 seconds per slot. With Praos implementation it might change, since Praos allows for shorter slots.

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Thanks for the clarification.

About he 20 second slot: Does the current data support this empirically? I wonder if there is a way to interrogate the network. Can’t find this on cardanoexplorer or adatracker.

Also, what’s your best guess to what the time slot interval might look like when we have Shelley?

What do you mean? You can see the 20 second intervals in the explorer:

And you always can find this info in the genesis block in the field "slotDuration": https://github.com/input-output-hk/cardano-sl/blob/8d25c2ad3ca2354af8f8c43a2972d1b9a31bf440/scripts/prepare-genesis/README.md

My best guess is that time slots might be 20 seconds or less when we have Shelley.


Sorry I must have totally missed this. Thank you again, Ruslan.