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.meta_keywords, 
  cscart_product_descriptions.meta_description, 
  cscart_product_descriptions.search_words, 
  cscart_product_descriptions.promo_text, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    12684, 12714, 13260, 13267, 6962, 6966, 
    6967, 6965, 6963, 6952, 6953, 6947, 
    6959, 3425, 6958, 6960, 6968, 6961, 
    6964, 6957, 6956, 6954, 6955, 6948, 
    6950, 6949, 13127, 12464, 12624, 12654, 
    13148, 13153, 12928, 12752
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00119

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "34.35"
    },
    "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": 34,
      "rows_produced_per_join": 34,
      "filtered": "100.00",
      "index_condition": "((`test2_gaseus`.`cscart_product_descriptions`.`product_id` in (12684,12714,13260,13267,6962,6966,6967,6965,6963,6952,6953,6947,6959,3425,6958,6960,6968,6961,6964,6957,6956,6954,6955,6948,6950,6949,13127,12464,12624,12654,13148,13153,12928,12752)) and (`test2_gaseus`.`cscart_product_descriptions`.`lang_code` = 'en'))",
      "cost_info": {
        "read_cost": "30.95",
        "eval_cost": "3.40",
        "prefix_cost": "34.35",
        "data_read_per_join": "155K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description",
        "meta_keywords",
        "meta_description",
        "search_words",
        "promo_text",
        "unit_name"
      ]
    }
  }
}