SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b151ad7b2b3e098b23146278b736319309afb2a3406de008236a82014da22b0f' 
  AND token = 'HrXagoNjGXjsH6tZ8qhS8BiZZPDzyZCLmKvWBBh+tA4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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