SELECT 
  feature_id, 
  variant_id, 
  value, 
  value_int 
FROM 
  cscart_product_features_values 
WHERE 
  product_id = 616 
  AND lang_code = 'de'

Query time 0.00049

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 41 Using where

Result

feature_id variant_id value value_int
128 5899
47 0 3.000
127 5895
30 5933
33 0 1500.000
32 0 50000.000
129 5913
121 0 450.000
122 0 4.500
46 0 85.000
178 6331