Optimizing auto-complete FULLTEXT SQL query

I have the following query which is used in order to do an auto-complete of a search box:

  SELECT *, MATCH (screen_name, name) AGAINST ('+query*' IN BOOLEAN MODE) AS SCORE 
  FROM users 
  WHERE MATCH (screen_name, name) AGAINST ('+query*' IN BOOLEAN MODE) 
  ORDER BY SCORE DESC LIMIT 3

I also have a FULL TEXT index on screen_name & name (together). When this table was relatively small (50k) this worked gre开发者_如何学运维at. Now the table is ~200k and it takes seconds(!) to complete each query. I'm using MySql MyISAM. Is this reasonable? What directions might I check in order to improve this as surely it doesn't satisfy the needs of an auto-complete query.

MYSQL Match against is really slow, you should look into alternatives like Sphinx Search Server.