SELECT 
  feature_id, 
  variant_id, 
  value, 
  value_int 
FROM 
  cscart_product_features_values 
WHERE 
  product_id = 10353 
  AND lang_code = 'en'

Query time 0.00034

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 45 Using where

Result

feature_id variant_id value value_int
42 145
21 96
24 107
30 128
22 100
23 6273
127 5895
128 5899
129 5902
20 6058 1.100
178 6306
19 241 0.700