SELECT 
  feature_id, 
  variant_id, 
  value, 
  value_int 
FROM 
  cscart_product_features_values 
WHERE 
  product_id = 514 
  AND lang_code = 'de'

Query time 0.00042

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 58 Using where

Result

feature_id variant_id value value_int
178 6309
176 6260
30 130
127 5895
128 5899
129 5902
135 5967
42 6251
149 0 5900988174722
124 0 5900988174722
135 5963
176 6270
176 6259
176 6262
176 6271
135 5968
176 6266