SELECT 
  product_id, 
  feature_id, 
  variant_id 
FROM 
  cscart_product_features_values 
WHERE 
  product_id IN (
    36661, 36662, 36663, 36664, 36665, 36666, 
    36667, 36668, 36669, 36670, 36671, 
    36672, 36673, 36674, 36675, 36676, 
    36677, 36678
  ) 
  AND feature_id IN (23264, 23692) 
  AND lang_code = 'vi'

Query time 0.00192

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_features_values",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY",
            "fl",
            "lang_code",
            "product_id",
            "fpl",
            "idx_product_feature_variant_id"
          ],
          "key": "idx_product_feature_variant_id",
          "key_length": "12",
          "used_key_parts": ["product_id", "feature_id", "lang_code"],
          "rows": 36,
          "filtered": 100,
          "attached_condition": "cscart_product_features_values.product_id in (36661,36662,36663,36664,36665,36666,36667,36668,36669,36670,36671,36672,36673,36674,36675,36676,36677,36678) and cscart_product_features_values.feature_id in (23264,23692) and cscart_product_features_values.lang_code = 'vi'",
          "using_index": true
        }
      }
    ]
  }
}