For SMBs, the budget is usually the main constraint, and you have to plan your solution carefully to consider the entire costs (including licenses) to fit in the budget. It's also possible that there is a budget spread across different years; in this case, you have to build a modular design where more parts can be added in the future to improve it (for example, the disaster recovery solution).

There can be some constraints on the devices, hardware, and software that can be used. For example, hold services must be recycled to optimize the investments.