structural:expansion, information:filtering
Modern software (post-1990s)

With regard to databases, POS systems are very demanding on their performance because of numerous submissions and retrievals of data - required for correct sequencing the receipt number, checking various discounts, membership, calculating subtotal, so forth - just to process a single sale transaction. The immediacy required of the system on the sale window such as may be observed at a checkout counter in a supermarket cannot be compromised. This places much stress on individual enterprise databases if there are just several tens of thousands of sale records in the database. Enterprise database Microsoft SQL Server, for example, has been known to freeze up (including the OS) entirely for many minutes under such conditions showing a "Timeout Expired" error message. Even a lighter database like Microsoft Access will slow to a crawl over time if the problem of database bloating is not foreseen and managed by the system automatically. Therefore, the need to do extensive testing, debugging and improvisation of solutions to preempt failure of a database before commercial implementation complicates the development.