SELECT 
  feature_id, 
  variant_id, 
  value, 
  value_int 
FROM 
  cscart_product_features_values 
WHERE 
  product_id = 9839 
  AND lang_code = 'de'

Query time 0.00037

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_feature_idx 3 const 47 Using where

Result

feature_id variant_id value value_int
24 107
30 240
42 6251
127 5895
128 5899
129 5903
135 5967
135 5963
135 5968
136 5973
149 0 5702326642494
176 6259
178 6308