SELECT 
  product_id, 
  feature_id, 
  variant_id 
FROM 
  cscart_product_features_values 
WHERE 
  product_id IN (
    49906, 49907, 49908, 49909, 49910, 49911, 
    49914, 49915, 49916, 49917, 49918, 
    49919
  ) 
  AND feature_id IN (24144, 25097) 
  AND lang_code = 'vi'

Query time 0.00367

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": "PRIMARY",
          "key_length": "6",
          "used_key_parts": ["feature_id", "product_id"],
          "rows": 48,
          "filtered": 77.08333588,
          "attached_condition": "cscart_product_features_values.product_id in (49906,49907,49908,49909,49910,49911,49914,49915,49916,49917,49918,49919) and cscart_product_features_values.feature_id in (24144,25097) and cscart_product_features_values.lang_code = 'vi'",
          "using_index": true
        }
      }
    ]
  }
}