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 (
    438300, 438310, 438321, 438143, 438152, 
    438177, 438180, 438188, 438195, 438212, 
    438218, 438052, 438076, 438086, 438088, 
    438091, 438098, 438102, 438114, 438117, 
    438128, 438135, 437939, 437947, 437960, 
    437962, 437993, 438009, 438012, 438027, 
    437839, 437842, 437850, 437861, 437876, 
    437879, 437895, 437901, 437836, 437741, 
    437755, 437768, 437794, 437811, 437653, 
    437661, 437686, 437696
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00090

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.08425304,
    "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": 48,
          "cost": 0.08425304,
          "filtered": 100,
          "attached_condition": "cscart_product_descriptions.product_id in (438300,438310,438321,438143,438152,438177,438180,438188,438195,438212,438218,438052,438076,438086,438088,438091,438098,438102,438114,438117,438128,438135,437939,437947,437960,437962,437993,438009,438012,438027,437839,437842,437850,437861,437876,437879,437895,437901,437836,437741,437755,437768,437794,437811,437653,437661,437686,437696) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}