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 (
    179151, 179150, 786964, 486447, 490232, 
    490233, 656537, 657781, 659382, 310629, 
    786962, 486444, 185586, 320712, 320923, 
    321175, 310630, 486446, 675690, 688310, 
    8, 9, 10, 786963
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00145

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.04252208,
    "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"],
          "loops": 1,
          "rows": 24,
          "cost": 0.04252208,
          "filtered": 100,
          "attached_condition": "cscart_product_descriptions.product_id in (179151,179150,786964,486447,490232,490233,656537,657781,659382,310629,786962,486444,185586,320712,320923,321175,310630,486446,675690,688310,8,9,10,786963) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}