SIMBAD is a service that provides reference data about celestial objects for astronomers that has been in operation for 50 years. Over this time astronomical data themselves have evolved because of the technological evolution of the observations, but also because of the evolution of software engineering. SIMBAD has gone through four major versions, each of which has been built using a different programming language, or other architecture, but with a long-term view to be scalable for future evolutions. For instance, the very first interactive version of SIMBAD, in 1981, allowed queries for data with a constraint on the sky coordinates. Now, in the 4 th version of SIMBAD, this service is still available, along with many other options. For each new version, in order to assure back-compatibility, the URLs and interfaces already used in the past are still available in parallel to the new version. The maintenance of such legacy software is necessary for the continuity of the service and to avoid problems for the many other community services that use SIMBAD. The support of such a software is challenging because it cannot be fully integrated with new developments. We will describe the range of different solutions that we use: specific redirections, hacks, interfaces, filters that are currently used for SIMBAD utilities.