SELECT 
  feature_id, 
  variant_id, 
  value, 
  value_int 
FROM 
  cscart_product_features_values 
WHERE 
  product_id = 479 
  AND lang_code = 'en'

Query time 0.00043

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_product_features_values ref lang_code,product_id,product_id_idx,product_feature_idx product_id 3 const 63 Using where

Result

feature_id variant_id value value_int
30 240
42 148
129 5903
127 5895
128 5899
24 108
135 5968
136 5972
135 5969
178 6308
124 0 5702326107542
149 0 5702326107542
135 5966
135 5970
135 5964
135 5965
176 6259