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 (
    20941, 20942, 20943, 20944, 20945, 20946, 
    20947, 20948, 20949, 20950, 20951, 
    20952, 20953, 20954, 20955, 20956
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00972

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 (20941,20942,20943,20944,20945,20946,20947,20948,20949,20950,20951,20952,20953,20954,20955,20956) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}

Result

product_id short_description full_description unit_name
20941 Microphone - hands-free, left<p>Part number 96575J6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20942 Microphone - hands-free, right<p>Part number 96576J6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20943 Cluster Assembly - Instrumentation<p>Part number 94013T1270</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20944 Switch assembly - multi-function<p>Part number 934B2T15804X</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20945 Unit Assembly-L.D.C<p>Part number 95300T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20946 Unit Assembly-L.D.C<p>Part number 95310T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20947 Unit assembly-integrated body control module<p>Part number 954B0T1091</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20948 Antenna Assembly-Smart Key<p>Part number 95460T1020</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20949 Antenna Assembly-Smart Key<p>Part number 95460T1100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20950 Antenna Assembly-Smart Key<p>Part number 95460T1300</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20951 Switch assembly - button start<p>Part number 93502T1100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20952 Unit Assembly - Wireless Charging<p>Part number 95560T1500</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20953 Unit Assembly - Identity Authentication<p>Part number 95590T1010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20954 Unit assembly-wireless communication<p>Part number 955B0T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20955 Battery-Video Recording System<p>Part number 95723T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20956 Module Assembly - Airbag Control<p>Part number 95910T1000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>