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 (
    21967, 21968, 21969, 21970, 21971, 21972, 
    21973, 21974, 21975, 21976, 21977, 
    21978, 21979, 21980, 21981, 21982
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00994

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 (21967,21968,21969,21970,21971,21972,21973,21974,21975,21976,21977,21978,21979,21980,21981,21982) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}

Result

product_id short_description full_description unit_name
21967 Hose & Pipe Assembly-Intercooler Inlet<p>Part number 282723N111</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21968 Cover Assembly-Engine<p>Part number 292403N200</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21969 bolt-eye<p>Part number 282433N000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21970 Protector-heat front, left<p>Part number 28791T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21971 Protector-Heat Rear<p>Part number 28795T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21972 BOLT<p>Part number 1140306207K</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21973 Electronic control unit (ECU)<p>Part number 391103N389</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21974 BRACKET-ECU<p>Part number 368753VAX0</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21975 Lower cover, back<p>Part number 29140T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21976 Tube-Fuel Feed<p>Part number 31310T6600</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21977 Tube-Fuel Vapor<p>Part number 31340T6600</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21978 Set-Oil Pump Assy<p>Part number 461004J250</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21979 Disc Set - 8LR Brave<p>Part number 456214J200</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21980 Carrier assembly - rear planet<p>Part number 457804J700</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21981 Carrier Assembly - Front Planet<p>Part number 457204J600</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21982 Carrier Assembly - Middle Planet<p>Part number 457504J600</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>