#### 23.2.7.7 Limitations Relating to Performance in NDB Cluster

[]()

 The following performance issues are specific to or especially pronounced in NDB Cluster:

* **Range scans.**  There are query performance issues due to sequential access to the [`NDB`](mysql-cluster.html) storage engine; it is also relatively more expensive to do many range scans than it is with either `MyISAM` or `InnoDB`.

* **Reliability of Records in range.**  The `Records in range` statistic is available but is not completely tested or officially supported. This may result in nonoptimal query plans in some cases. If necessary, you can employ `USE INDEX` or `FORCE INDEX` to alter the execution plan. See [Section 8.9.4, “Index Hints”](index-hints.html), for more information on how to do this.

* **Unique hash indexes.**  Unique hash indexes created with `USING HASH` cannot be used for accessing a table if `NULL` is given as part of the key.

