What happens if a validator node “drops out” or unregisters during an epoch?

If a validator node “drops out” and stops verifying transactions during an epoch, or stops responding for whatever reason, consensus will see that they have timed out and move on. However, this may slow down the speed of the network, as other validators continue to wait for that validator to propose rounds or vote in consensus, without response. Their emission rewards will also rapidly go to zero, and the market price of that validator’s Liquid Stake Unit (LSU) tokens may change and stakers may quickly remove their stake and allow other validators to move into the top-100.

This is why it’s important to understand the validator community and stake to those validators that are reliable, trustworthy, and performant. See How should I choose validators to stake to for guidance on this.

If a validator unregisters during an epoch, they will simply be replaced by the next validator with the most amount of staked XRD delegated to their validator component. E.g. if validator #59 drops out before an epoch boundary, they will be replaced by validator #101, who would then become validator #100.

Furthermore, there is no need for a “buffer” of validator nodes waiting to jump in as Radix consensus does not actually require 100 validator nodes – that’s just the upper limit.

As the Radix Public Network does not require 100 validator nodes, and there are strong incentives for stakers to delegate to nodes with high participation in consensus rounds, there is no need to have a set of validators-in-waiting from the perspective of network liveness.

Further reading: