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 (
    21935, 21936, 21937, 21938, 21939, 21940, 
    21941, 21942, 21943, 21944, 21945, 
    21946, 21947, 21948, 21949, 21950
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00070

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 (21935,21936,21937,21938,21939,21940,21941,21942,21943,21944,21945,21946,21947,21948,21949,21950) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}

Result

product_id short_description full_description unit_name
21935 Bearing pair set - connecting rod<p>Part number 230603N541</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21936 crankshaft<p>Part number 231113NTA1</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21937 Piston & Pin & Snap Ring Assembly<p>Part number 230413NTA1</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21938 Piston & Pin & Snap Ring Assembly<p>Part number 230413NTB1</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21939 Piston & Pin & Snap Ring Assembly<p>Part number 230413NTC1</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21940 radiator assembly<p>Part number 25310T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21941 radiator assembly<p>Part number 253L0T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21942 Hose assembly - radiator, top<p>Part number 25414T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21943 Hose assembly - radiator, lower part<p>Part number 25415T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21944 Hose Assembly - Water Vent<p>Part number 254683N130</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21945 clip-hose<p>Part number 254814Q000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21946 connector<p>Part number 25485F3300</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21947 connector<p>Part number 25485T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21948 connector<p>Part number 25485T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21949 Hose Assembly - Inlet<p>Part number 254L4T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21950 Hose Assembly-Outlet<p>Part number 254L5T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>