If you are using asynchronous requests to upload data into an APEX_COLLECTION, you will end up with an ORA-00001: unique constraint violated (APEX_040100.WWV_FLOW_COLLECTION_MEMBERS_PK) . The reason is simple, sometimes APEX tries to insert the same value (WWV_FLOW_COLLECTION_MEMBERS$.SEQ_ID). A workaround consist of managing queues on the server side.
This summer, I discovered a bug in the billing module of Google AdWords . Working with the Google Security Team, we have been able to reproduce and fix the problem. Thus, my name is found on the Google Security Hall of Fame . Usually, I don't dig for exposure, but when I do, I do it Béton! ;)