CKPool.

CKPool was ckpool.org, a shared mining poolMining poolA group of miners who share the work of finding blocks and split the rewards, so each gets paid steadily instead of rarely. run by Con Kolivas, who created the cgminer mining software and runs Solo CK. He opened it to the public as a test on 19 April 2017, and its first block came on 23 August 2017. Unlike Solo CK, its miners shared each reward. It isn’t KanoPool, which was called CKPool when it opened in 2014.

It paid miners straight from the block. Each block’s first transaction paid up to 150 miners at once, the 100 biggest and 50 of the smaller ones in turn, so the pool never held anyone’s earnings. Those are the miners’ shares of the reward, separate from the transactions confirmed inside the block.

It stayed small: 79 of its 86 blocks came in 2018, and only four after that. On 10 May 2020 a server overload cost a Solo CK miner a block, and Kolivas said he would close both services after the halving, calling ckpool.org’s hashrateHashrateHow many guesses a second all of Bitcoin's miners make together. More hashrate makes the network harder to attack. “appallingly small” and saying his heart had “really not been in it”. He closed ckpool.org the next day, 11 May 2020, and moved its remaining miners to Solo CK, which he kept open after all.