If the list of search terms is very large, then the LISTFIND() function may execute somewhat more slowly. The best way to address this is to minimize the amount of text being searched. One alternative is to limit your search to a specific field of interest, like:
EXTRACT IF LISTFIND("list.txt", name)
If the field often contains many trailing blanks, then an even better solution is to remove trailing blanks, like:
EXTRACT IF LISTFIND("list.txt", trim(name))