SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.product, 
  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 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    4003, 4002, 4006, 4001, 4000, 4598, 2510, 
    2507, 2508, 2511, 2509, 3753, 489, 416, 
    3182, 3181, 494, 488, 492, 497, 495, 
    3656, 1610, 1606, 1608, 1609, 1676, 
    1675, 1607, 1677, 491, 1737, 1736, 100, 
    95, 6430, 6431, 7254, 7255, 4050, 4051, 
    4602, 4049, 4034, 4048, 4419, 4601, 
    4422
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00127

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "33.61"
    },
    "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": "((`dbggbern`.`cscart_product_descriptions`.`product_id` in (4003,4002,4006,4001,4000,4598,2510,2507,2508,2511,2509,3753,489,416,3182,3181,494,488,492,497,495,3656,1610,1606,1608,1609,1676,1675,1607,1677,491,1737,1736,100,95,6430,6431,7254,7255,4050,4051,4602,4049,4034,4048,4419,4601,4422)) and (`dbggbern`.`cscart_product_descriptions`.`lang_code` = 'en'))",
      "cost_info": {
        "read_cost": "28.81",
        "eval_cost": "4.80",
        "prefix_cost": "33.61",
        "data_read_per_join": "183K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "product",
        "short_description",
        "full_description"
      ]
    }
  }
}