[Pharo-users] best solution to store data

Hello, I want to try to make a financial app for a organisation. There are some 50 customers so also 50 invoices a year. Then the payments . Also 50 a year. Cash and bank accounts . Every month some 10 - 20 things. So on my disk on the programm I now use it costs me some 30 - 50 Kb a year. What are my options for storage of those data. I could use a database , but I wonder if there are more and better options. Roelof