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 (
    432489, 401596, 415005, 453645, 431006, 
    439809, 446683, 453556, 416409, 459420, 
    449993, 452526, 427885, 449587, 440855, 
    429487, 429075, 419365, 404172, 419514, 
    437962, 413207, 435238, 413616, 427837, 
    433931, 457584, 439522, 404231, 420223, 
    403855, 453787, 454909, 403015, 438963, 
    450825, 446646, 435981, 434868, 409956, 
    443424, 427907, 457801, 436128, 436002, 
    421748, 432913, 421122
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00166

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 (432489,401596,415005,453645,431006,439809,446683,453556,416409,459420,449993,452526,427885,449587,440855,429487,429075,419365,404172,419514,437962,413207,435238,413616,427837,433931,457584,439522,404231,420223,403855,453787,454909,403015,438963,450825,446646,435981,434868,409956,443424,427907,457801,436128,436002,421748,432913,421122) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}