SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5c29f03dfc7308842f04a3580dd33b233cfdfbfd5a05d398875f4f204996d8b' 
  AND token = '4BI43+EKeWBtCZ8oanMFCRgBIMGKusYlIbSmsDYg9pg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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