Connect 4 is one of those games that looks simple until you realize it was solved in 1988 and the optimal strategy still takes serious compute to run in real time.

Not that serious, since you can solve the 7x6 game from scratch on a typical 2013 single core in a few minutes (and in 67s on an Apple M2):

    $ time ./SearchGame < input.root 
    Fhourstones 3.2 (C)
    Boardsize = 7x6
    Using 8306069 transposition table entries of size 8.
    
    Solving 0-ply position after  . . .
    44+26
    45+28
    42+27
    47+26
    4-29
    +29
    score = 5 (+)  work = 29
    1479113766 pos / 139494 msec = 10603.4 Kpos/sec
    - 0.249  < 0.125  = 0.027  > 0.191  + 0.408
    
    real    2m24.904s