Tag management in Apollo
One of the most requested features as far as Apollo's CRM was the possibility to manage contact tags within Apollo.
One typical scenario is having a contact with a mispelled tag: Apollo's auto-completion basically means that that spelling mistake was given as an option to the users every time.
Implementing tag management was trickier than one can imagine. One of the big issues is about visibility of contacts. For example, you might have Contact X with tags A, B, C and Contact Y with tags C, D and E. Assume you only have access to contact X. If you change tag A, it's all fine.