SELECT 
  product_id, 
  short_description, 
  full_description 
FROM 
  cscart_product_descriptions 
WHERE 
  product_id IN (15430, 13108, 13825, 11920) 
  AND lang_code = 'en'

Query time 0.00020

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "product_id"],
      "key": "product_id",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "rows": 4,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (15430,13108,13825,11920)",
      "attached_condition": "cscart_product_descriptions.lang_code = 'en'"
    }
  }
}