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 (
    21277, 21278, 21279, 21280, 21281, 21282, 
    21283, 21284, 21285, 21286, 21287, 
    21288, 21289, 21290, 21291, 21292
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00043

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 (21277,21278,21279,21280,21281,21282,21283,21284,21285,21286,21287,21288,21289,21290,21291,21292) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}

Result

product_id short_description full_description unit_name
21277 Wiring Assembly - FEM<p>Part number 91840T6040</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21278 lower cover<p>Part number 919B5T6300</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21279 Wiring assembly-start solenoid extender<p>Part number 91875T6010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21280 Wiring Assembly-Battery<p>Part number 91850T6010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21281 Wiring assembly to engine ground<p>Part number 91861T6010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21282 Wiring assembly-transmission ground<p>Part number 91862T6010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21283 Upper Cover - Fuse & Relay Engine<p>Part number 91956T6300</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21284 Junction Block-Sub<p>Part number 91945T6310</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21285 Wiring Assy - Tailgate<p>Part number 91650T6010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21286 Protector-wiring<p>Part number 91961T6270</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21287 Protector-wiring<p>Part number 91961T6280</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21288 Protector-wiring<p>Part number 91961T6290</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21289 Protector-wiring<p>Part number 91961T6480</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21290 Protector-wiring<p>Part number 91961T6470</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21291 Protector-wiring<p>Part number 91961T6300</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21292 Protector-wiring<p>Part number 91970D2140</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>