MMBase

If you execute the following jsp, about 4000 times:
  <mm:listcontainer path="people,classrel,classes">
        <mm:maxnumber value="1" />
        <mm:sortorder field="classrel.lastlogin" />
        <mm:list />
      </mm:listcontainer>

The sorteorder is essential.

Then your mmbase ends up in a unusable state because very many things fail because of a stackoverflow exceptions
at java.util.Collections$UnmodifiableMap$UnmodifiableEntrySet$1.(Collections.java:1340)
at java.util.Collections$UnmodifiableMap$UnmodifiableEntrySet.iterator(Collections.java:1339)
at java.util.Collections$UnmodifiableMap$UnmodifiableEntrySet$1.(Collections.java:1340)
at java.util.Collections$UnmodifiableMap$UnmodifiableEntrySet.iterator(Collections.java:1339)
at java.util.Collections$UnmodifiableMap$UnmodifiableEntrySet$1.(Collections.java:1340)