This paper describes the methodology we use in the design of a complex object server application for the Amoeba distributed operating system. We use the topdown design that was suggested by Pamas, in which a model is turned into an implementation b y gradually adding details. We describe the abstraction levels that show up if going from a specification of the behaviour towards an implementation, and we show our methodology in which performance will be measured (instead of estimated) whereas the system has not yet been functionally implemented in its entirety.