SELECT 
  feature_id, 
  variant_id, 
  value, 
  value_int 
FROM 
  cscart_product_features_values 
WHERE 
  product_id = 406 
  AND lang_code = 'de'

Query time 0.00047

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 59 Using where

Result

feature_id variant_id value value_int
135 5965
176 6262
127 5895
128 5899
129 5902
30 128
42 148
135 5969
135 5970
178 6306
135 5966
24 108
176 6260
176 6270
135 5964
135 5968