Writing to a DKNF database, but reading from a de-normalized table for performance?
Use the full normalized database, scan which queries need more performance than this model can give them and create materialized views on them. If the data is very volatile, having them fast refreshing introduces some overhead but you know the value and validity of your data, that is protected by the database. Oracle handles this very nice.

You queries remain using the normalized tables and Query Rewrite will take care of the usage of the Materialized Views, when appropriate. When the Materialized Views are not fresh, the queries fall back to the original tables.

For docu see Materialized View Concepts and Architecture