SELECT 
  feature_id, 
  variant_id, 
  value, 
  value_int 
FROM 
  cscart_product_features_values 
WHERE 
  product_id = 9821 
  AND lang_code = 'en'

Query time 0.00058

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 44 Using where

Result

feature_id variant_id value value_int
30 240
127 5895
128 5899
129 5902
178 6308
42 145
22 98
23 101
20 6059 1.000
24 107
21 96
19 5989 0.600