When using many CPFs with language options (boolean, dropdown, etc.), these language values are retrieved from the DB on an individual basis by phpbb/profilefields/lang_helper.php

This means that the number of queries on viewtopic.php (and possibly other places) can skyrocket, as the number of queries increases by unique users on page * active cpf with lang options

The result will be something like this:
Page generated in 0.9048 seconds with 96 queries + 5 queries returning data from cache

With dozens of queries like:
SELECT option_id, lang_value FROM phpbb_profile_fields_lang WHERE field_id = 31 AND lang_id = 1 AND field_type = '4' ORDER BY option_id

This could and should be much more efficient.