The Spitzer Heritage Archive will host all the raw and final reprocessed science and calibration data products from the observations made by Spitzer Space Telescope. The interactive web interface will give users the tools to search the database and explore their search results interactively. We also reuse the existing software and services and pay close attention to the re-usability of the newly developed system, making it easy to expand and adopt new technology in the future. This paper discusses our design principles, system architecture, reuse of the existing software, and reusable components of the system.