SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '541909b176756f94db91bc236f3d1954be71a82ae1fd12dbedae47efbdb44e41' 
  AND token = '6pHmkvlKrLFRXQgr3btUZ6lwbZUJwbbbqK4AKRbmCQM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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