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 (
    21229, 21230, 21231, 21232, 21233, 21234, 
    21235, 21236, 21237, 21238, 21239, 
    21240, 21241, 21242, 21243, 21244
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00047

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 (21229,21230,21231,21232,21233,21234,21235,21236,21237,21238,21239,21240,21241,21242,21243,21244) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}

Result

product_id short_description full_description unit_name
21229 Protector-wiring<p>Part number 91961T6020</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21230 Protector-wiring<p>Part number 91961T6030</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21231 Protector-wiring<p>Part number 91961T6040</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21232 BOLT<p>Part number 1128106166B</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21233 Fuse-60(A)<p>Part number 1879001126</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21234 Cover-junction box, lower part<p>Part number 919B5T6200</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21235 Wiring Assembly-Front<p>Part number 91202T6150</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21236 Upper Cover Assembly - Fuse & Relay<p>Part number 919C5T6200</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21237 lower cover<p>Part number 919B5T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21238 Upper Cover - Engine Room Box<p>Part number 91956T6101</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21239 Protector-wiring<p>Part number 91961T6050</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21240 Protector-wiring<p>Part number 91961T6060</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21241 Protector-wiring<p>Part number 91961T6070</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21242 Protector-wiring<p>Part number 91961T6080</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21243 Protector-wiring<p>Part number 91961T6090</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21244 BOLT<p>Part number 1141506207B</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>