SELECT 
  feature_id, 
  variant_id, 
  value, 
  value_int 
FROM 
  cscart_product_features_values 
WHERE 
  product_id = 10355 
  AND lang_code = 'en'

Query time 0.00054

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 100 Using where

Result

feature_id variant_id value value_int
30 128
178 6306
22 100
23 6273
19 241 0.700
42 145
21 96
24 107
127 5895
128 5899
129 5902
152 6094
152 6093
20 6058 1.100
152 6096
152 6092
152 6095
152 6091
152 6090
152 6089
152 6088
152 6097
152 6100
152 6101
152 6105
152 6106
152 6107