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 (
    1096, 1098, 1095, 1078, 1086, 1099, 886, 
    884, 1055, 1056, 1057, 1058, 786, 789, 
    792, 699, 777, 774, 781, 1024, 1025, 
    1028, 1050, 1051, 1052, 1049, 1067, 
    1033, 1034, 1037, 1035, 1036, 1038, 
    1032, 1062, 1061, 1060, 1063, 1059, 
    1064, 1066, 976, 978, 968, 971, 636, 
    969, 972
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00124

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "115.21"
    },
    "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": 48,
      "rows_produced_per_join": 48,
      "filtered": "100.00",
      "index_condition": "((`cscart`.`cscart_product_descriptions`.`product_id` in (1096,1098,1095,1078,1086,1099,886,884,1055,1056,1057,1058,786,789,792,699,777,774,781,1024,1025,1028,1050,1051,1052,1049,1067,1033,1034,1037,1035,1036,1038,1032,1062,1061,1060,1063,1059,1064,1066,976,978,968,971,636,969,972)) and (`cscart`.`cscart_product_descriptions`.`lang_code` = 'ru'))",
      "cost_info": {
        "read_cost": "105.61",
        "eval_cost": "9.60",
        "prefix_cost": "115.21",
        "data_read_per_join": "219K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description",
        "unit_name"
      ]
    }
  }
}