SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3686902e7fbc3834b558818bf0f6d9cad917f4c102c0018d23fc60af26be1254' 
  AND token = 'C7XHuKL6u8nPZpCvzFyPXL6WZAPK1MJxhGFDsZNJfDk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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