SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75b5ac01f2da2a36d53d811c75680373cd77f292095153b05db686480a61523a' 
  AND token = 'xxqDC6ymlciW4EkY0QkvxbfhgRPn/sryOVwA94cWaO0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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