The Lean approach is used to best match a product/service to market needs, as well as to verify the correctness of business assumptions. In the Lean iterative approach, these assumptions may change very often. For example, creating a web application can turn into the design of a mobile application or, moreover, grow into a whole server system which supports hundreds of thousands of requests per minute.
Therefore, it is advisable to entrust the created solutions to a partner who understands the Lean approach and has a wide range of technologies which can be used not only in current, but also future design requirements. Thanks to this approach, technology will not limit you and you will not be forced to change your partner if the range of supported technology stacks is insufficient for you.