SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.short_description, 
  IF(
    cscart_product_descriptions.short_description = '' 
    OR cscart_product_descriptions.short_description IS NULL, 
    cscart_product_descriptions.full_description, 
    ''
  ) AS full_description, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    286, 278, 280, 282, 247, 255, 256, 257, 
    249, 250, 251, 252, 253, 254, 248, 245
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00164

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_descriptions",
          "access_type": "range",
          "possible_keys": ["PRIMARY", "product_id"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["product_id", "lang_code"],
          "rows": 16,
          "filtered": 100,
          "index_condition": "cscart_product_descriptions.product_id in (286,278,280,282,247,255,256,257,249,250,251,252,253,254,248,245) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}