SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21e76ba1c7bd839caf1cfd9807de60c56078a73020f6e61badaf0fcce771f2aa' 
  AND token = 'l5YXuYUOspbuId/7t1lhwg5fDEj0FhDGOYc21fnM6yA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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