A tight timeline is definitely the first challenge that came into my mind, as this version had been kick-started just a few months after the previous version launched. Therefore, there were overlaps between the two versions, which means tasks and design works were doubled.
The most challenging thing always come from human factors - cooperate and negotiate with external parties, such as adopting new branding visual elements, balancing the proportion between promotion items and contents. Besides the UI and cooperation matters, and another challenging part is to cope with difficult system logic and flow handling.
Account-related function had expended a lot in app 3.0 compared with app 2.0. Here is one of the use cases of account merge flow. Before drafting the flow, as a designer, we had a really clear understanding of the logic and limitation, such as "which account will be the dominion?", "When will exceptional case happen".