granted your oltp app is going to generate a large number of distinct queries, but how many different actual query statements are there on the table?

select something where user_id = 34, and
select something where user_id = 35

may be different queries but odds are they will be treated the same.

if you can work with the apps people to se what queries are being run on the table (hopefully not too many), you could just explain plan them all :)