SELECT 
  feature_id, 
  feature_type 
FROM 
  cscart_product_features 
WHERE 
  feature_id IN (551, 552, 18, 549, 550, 548)

Query time 0.00016

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_product_features ALL PRIMARY 39 Using where

Result

feature_id feature_type
551 S
18 E
550 E
552 M
549 S
548 S