SELECT 
  object_id, 
  thread_id, 
  type, 
  object_type 
FROM 
  cscart_discussion 
WHERE 
  1 
  AND object_id = 19 
  AND object_type = 'A'

Query time 0.00062

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE Impossible WHERE noticed after reading const tables