SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    10566, 10567, 10572, 10575, 10581, 10582, 
    10583, 10584, 10588, 10589, 10590, 
    10595, 10596, 10602, 10612, 10613
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00043

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "product_id", "idx_product_lang"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["product_id", "lang_code"],
      "rows": 16,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (10566,10567,10572,10575,10581,10582,10583,10584,10588,10589,10590,10595,10596,10602,10612,10613) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}