SELECT 
  feature_id, 
  variant_id, 
  value, 
  value_int 
FROM 
  cscart_product_features_values 
WHERE 
  product_id = 567 
  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 37 Using where

Result

feature_id variant_id value value_int
33 0 500.000
32 0 1000.000
30 212
67 225
27 139 0.035
49 0 150.000
127 5895
128 5899
129 5913
178 6325