SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42538e50ae499705f02dbf7fd446ea63e094c9618f1fab6eef3b170f6f978331' 
  AND token = 'BJgWV+eeUWf2q5Aygt8LnMEZqMMkEPhOwulrKvcaFZ8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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