SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '438c8df2688a294bf6a74a4d4012e7c04034f419d577f13e76ed33b763b9320e' 
  AND token = 'KHniTlg9Y6slXezsU0kwRusosU2kyTrpcDduSE7GSWM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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