A bartender needs to have his own "top twenty" memorized at a bare minimum. These are his most popular requests that his particular crowd always asks for on a regular basis. In addition' he needs another 20-25 that he only needs minimal prompting on that are second-tier requests.
If you are a bartender, you should know a large variety of mixed drink recipes, but maybe your friend is a bartender in a bar that serves mostly beer and shots and he does not need to know a bunch of recipes.