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 (
    6454, 6535, 6792, 7705, 7731, 10133, 
    6553, 6666, 10039, 10095, 8867, 10012, 
    6571, 6732, 7520, 6551, 6683, 6744, 
    7745, 6573, 6587, 6756, 6782, 7517, 
    7529, 10120, 6673, 6714, 7542, 7677, 
    8345, 8976, 6495, 6582, 6583, 6680, 
    6789, 6796, 7584, 10148
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00171

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "28.33"
    },
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "product_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "product_id",
        "lang_code"
      ],
      "key_length": "9",
      "rows_examined_per_scan": 40,
      "rows_produced_per_join": 40,
      "filtered": "100.00",
      "index_condition": "((`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_descriptions`.`product_id` in (6454,6535,6792,7705,7731,10133,6553,6666,10039,10095,8867,10012,6571,6732,7520,6551,6683,6744,7745,6573,6587,6756,6782,7517,7529,10120,6673,6714,7542,7677,8345,8976,6495,6582,6583,6680,6789,6796,7584,10148)) and (`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_descriptions`.`lang_code` = 'en'))",
      "cost_info": {
        "read_cost": "24.33",
        "eval_cost": "4.00",
        "prefix_cost": "28.33",
        "data_read_per_join": "182K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description",
        "unit_name"
      ]
    }
  }
}