Is the fast of one who works in a shop that sells alcohol and pork valid or invalid?

It is not permissible to work in a place where alcohol and pork are sold, especially if the person sells these forbidden items or assists in their sale. Fasting is abstaining from things that break the fast from dawn until sunset with the intention, and if these conditions are met, the fast is valid. However, engaging in forbidden acts while fasting deprives one of the reward and merit, as the Prophet, peace and blessings be upon him, said: "Whoever does not give up false speech and acting upon it and ignorance, Allah has no need of his giving up his food and drink." Therefore, your fast is not invalid, but it is without fruit or reward, and you must repent and distance yourself from this profession.