* Many layers. Sometimes it is hard to get something done. Too early to have such a structure in such an young company.
* Salary. The prices in Lisbon are quite high and the salary, (while OK by Portuguese IT standards) barely allows saving.
Generally speaking (not Farfetch-related), if you're an expat planning to move to Lisbon, make sure you understand well the budget constraints. Also, if you have a partner that isn't in an IT-field, take into account the possibility that finding any other job will be extremely hard.