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 (
    21599, 21600, 21601, 21602, 21603, 21604, 
    21605, 21606, 21607, 21608, 21609, 
    21610, 21611, 21612, 21613, 21614
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00065

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "product_id", "idx_product_lang"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["product_id", "lang_code"],
      "rows": 16,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (21599,21600,21601,21602,21603,21604,21605,21606,21607,21608,21609,21610,21611,21612,21613,21614) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}

Result

product_id short_description full_description unit_name
21599 Clamp-Hose<p>Part number 1471176006B</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21600 Cleaner Assembly-Air<p>Part number 28110T1220</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21601 Cover - Air Cleaner<p>Part number 28111T1210</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21602 Body-Air Cleaner<p>Part number 28112T1210</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21603 Filter - Air Cleaner<p>Part number 28113T1210</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21604 Hose Assembly - Air Intake<p>Part number 28130T1210</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21605 Hose-intake air ‘A’<p>Part number 28138T1210</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21606 Duct Assembly - Air<p>Part number 28210T1210</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21607 hose-reservoir<p>Part number 282922T010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21608 clip-hose<p>Part number 2548223006</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21609 Hose-Intercooler Inlet A<p>Part number 282812T000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21610 Hose & Pipe Assembly-Intercooler Inlet<p>Part number 282722T000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21611 Hose-Valve 3WAY<p>Part number 282932T010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21612 Warm-Up Catalytic Converter Module Assembly<p>Part number 285102T200</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21613 Electronic control unit (ECU)<p>Part number 391212TRD5</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21614 Bracket-PCU<p>Part number 391502TRG0</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>