SELECT 
  feature_id, 
  variant_id, 
  value, 
  value_int 
FROM 
  cscart_product_features_values 
WHERE 
  product_id = 10140 
  AND lang_code = 'de'

Query time 0.00038

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 48 Using where

Result

feature_id variant_id value value_int
128 5899
21 96
30 240
42 146
75 243
24 107
129 5902
127 5895
23 6297
20 6059 1.000
178 6308
19 5989 0.600
22 100