SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b21d28f4991f6139238235b8e1a40d406c13a00ebbb735e313371d1ccc5f986c' 
  AND token = '8hC9DIjIblEzGYsu3VIQNfz5iBRkIrZZk0/SzQjXKow=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}