This paper presents experience gathered through the implementation of a CORBA-based localization system for an office environment. The localization system simultaneously preserves the fine-grained object-oriented structure of the system and achieves efficient performance. The presented study is a practical lesson concerning the implementation of a scalable, information-dissemination system. The key idea is to represent a large observable collection of objects by a repository that provides access to them both as individual CORBA objects and as data records. The proper use of this duality may have a substantial impact on the overall system performance. The repository is equipped with a scalable notification mechanism built around the concepts of a notification dispatcher and a notification tree. Fundamental features of the proposed solution are illustrated by a performance study and a representative application.