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 (
    18301, 18302, 18303, 18304, 18305, 18306, 
    18307, 18308, 18309, 18310, 18311, 
    18312, 18313, 18314, 18315, 18316
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00181

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 (18301,18302,18303,18304,18305,18306,18307,18308,18309,18310,18311,18312,18313,18314,18315,18316) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}

Result

product_id short_description full_description unit_name
18301 Ring-Snap<p>Part number 4565647126</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
18302 Ring-Snap<p>Part number 4565647127</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
18303 Ring-Snap<p>Part number 4565647128</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
18304 Ring-Snap<p>Part number 4565647129</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
18305 Ring-Snap<p>Part number 4565647130</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
18306 Ring-Snap<p>Part number 4565647131</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
18307 Ring-Snap<p>Part number 4565647132</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
18308 Disc Set-27 Brakes<p>Part number 4565147150</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
18309 spring-cushion<p>Part number 4562747000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
18310 Spring-27 Brake Return<p>Part number 4566547000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
18311 Hub-6 Clutch & Low Reverse Brake<p>Part number 4568047000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
18312 Shaft Assembly - Input<p>Part number 4570147600</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
18313 gear-front line<p>Part number 4571047000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
18314 Carrier Assembly - Front Planet<p>Part number 4572047600</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
18315 Gear Assy-Mid Line<p>Part number 4574047000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
18316 seal ring<p>Part number 4570547000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>