Absolute speed depends on the machine resource and the low-level optimization. If you take MCTS it is "enough fast" considering it has already beat Lee Sedol.
There are multiple means to measure the speed. Blind search is "fast" re: node expansion but takes exponential time to find a solution and quite likely exhausts memory. Search with heavy heuristic functions has "slow" expansion but can solve the problem quickly, despite the cost of evaluating them, since it can prune a large part of the state space and expands fewer nodes. Only the latter is practically meaningful.
Just read the classical AI textbooks like AIMA first, then [this one](https://www.amazon.co.uk/Heuristic-Search-Applications-Stefa...) if you want to know more. Maybe [this short paper](https://www.cs.cmu.edu/~maxim/files/searchcomesofage_aaai12_...) may give you the gist.