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 (
    20893, 20894, 20895, 20896, 20897, 20898, 
    20899, 20900, 20901, 20902, 20903, 
    20904, 20905, 20906, 20907, 20908
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00039

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 (20893,20894,20895,20896,20897,20898,20899,20900,20901,20902,20903,20904,20905,20906,20907,20908) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}

Result

product_id short_description full_description unit_name
20893 Wiring assembly - rear door right<p>Part number 91630T1020</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20894 Terminal-Battery (+)<p>Part number 91982C7010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20895 Upper Cover - Fuser Blink Box<p>Part number 91956T1400</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20896 Wiring Assembly - FEM<p>Part number 91840T1060</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20897 Upper Cover - Fuser Blink Box<p>Part number 91956T1420</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20898 Wiring Assembly-Battery<p>Part number 91850T1010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20899 Wiring assembly to engine ground<p>Part number 91861T1020</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20900 Wiring assembly-transmission ground<p>Part number 91862T1010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20901 Sensor Assy-Rear Height<p>Part number 55830T1100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20902 Tape-Double Adhesive<p>Part number 92127J6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20903 Lamp bracket-head, left<p>Part number 92151T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20904 Lamp bracket-head, right<p>Part number 92152T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20905 Lamp assembly-head, left<p>Part number 92101T1100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20906 Lamp assembly-head, right<p>Part number 92102T1100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20907 Subassembly - headlamp, left<p>Part number 92103T1100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20908 Subassembly - headlamp, right<p>Part number 92104T1100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>