short of knowing how your schema is designed Im not sure if anyone can help
I dont think you should see a signigifcant performance problem doing what you want. however a great deal would depend on how your tables(s) were designed, indexed, and how good your queries are.
so as a first step it may help if you detail your table(s) design (identifying the keys and/or realtionships) AND the queries you are using.
do you jnow where the time is being consumed (is it the db, or is it retrieving the information via AJAX (is it a db server, a web server or communications issue)