# List Indexes

> As explained in the Indexes page, the eXtremeDB`list` index can be declared to allow applications to iterate over the objects of a class without regard to any particular order. If no other index is defined for a given class, then a `list` index will be created implicitly.

> As with `autoid` indexes the index value for a new database object is inserted into the list index at the moment it is created and is never changed. (Note that this is different from other types of indexes. Normally new values are inserted into the index (hash table or tree structure) when the transaction within which these values are created or updated is committed or when a transaction checkpoint is performed.)