SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b28c0962fb355f01707ab3edcb00a76c1887e266783e9451b94927aee892acb5' 
  AND token = 'nKi/zsXxyyr4wf0Mb+8WiVBpDkiQuWYcxH+Haqo5JhU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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