The Tycoon Store Protocol (TSP) specifies a clean interface between the frontend and the backend of fully integrated persistent environments. In contrast to high-level relational or object-oriented database languages, TSP is based on a low level, untyped, but highly flexible tagged store model that is particularly well-suited for the implementation of higher-order persistent polymorphic languages. We describe the TSP operations in some detail and give insight into TSP’s design rationale. We also report on the existing set of TSP-compliant backends including TSP adaptors to commercial object stores. A TSP client can choose dynamically between these backendsand it is possible to exchange complex object graphs between all TSP-compliant stores via a platform-independent external data representation.