SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.short_description, 
  IF(
    cscart_product_descriptions.short_description = '', 
    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 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (3924) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00015

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "const",
      "possible_keys": ["PRIMARY", "product_id"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["product_id", "lang_code"],
      "ref": ["const", "const"],
      "rows": 1,
      "filtered": 100
    }
  }
}

Result

product_id short_description full_description meta_keywords meta_description search_words promo_text
3924 <p> UNI I.S. battery for EVX-531, EVX-534, EVX-539, VX-451, VX-454, VX-459. For use with the VAC-UNI and VAC-6058 (MUC) chargers.</p> VX-450IS Battery, EVX-530IS Battery, Vertex Standard OEM Batteries, FNBV134IS, FNBV134LIIS, FNB-134LIIS, FNB-V134, Vertex IS battery, Vertex IS batteries, Vertex Standard IS battery, Vertex Standard IS batteries