SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4594ab57501e713c675dff48f10564ecfb067db37a508668efdf1d7a76368b51' 
  AND token = '2PjN6KzrTO0SfLamzNXkia5XmHHbR6UgrUfhJZl+3xA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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