Smartcards are becoming the most secure and cheap portable computing device today. They have been used successfully in many applications involving money, proprietary and personal data. But, as smartcards get more powerful and become multiapplication, the need for database management arises. The design of very small databases for smartcards is constrained by the peculiar features of the physical medium. Also, smartcards have severe hardware limitations, which make traditional database technology irrelevant. The major task is to scale down the database techniques so that they can perform well under these severe constraints. This paper gives an in-depth analysis of the constraints and proposes a solution, PicoDBMS, which is based on highly compact data structures, optimizing the RAM consumption during query execution, and speci_c techniques for atomicity and durability in transactions.