question

Please let me rephrase your case first in case I misunderstood something, please correct me if I were wrong:

1. The “Clients” you talked about equals to “Player”, and I will use “Player” instead of “Clients” next.
2. A Player can possess 0-10 Characters
3. A Character can have 0-10 Crews, however, each Crew only belongs to 1-4 Characters
4. A Crew can have 0-5 Ships, and each Ship only belongs to One Crew.
5. A Player can have several Friendships (0-*) with other players, each Friendship contains two players.
6. A Player can have other information like name, currency, appearance data, etc.

If that’s your case and I didn’t misunderstand anything, I believe that’s possible in PlayFab:

For 2, PlayFab provides the Character feature, which is suitable for your case, please navigate to this blog post to learn about more: Get In Character with PlayFab

For 3, each Character can have their own Player Data, Objects (Entity Objects), etc., you can store the Crew data as Player Data/Objects (It is recommended that all new Titles utilize Entity objects, as that will give the most flexibility and performance for your game). For the case that each Crew only belongs to 1-4 Characters, you may need to add some additional server/client side logic to make that happen.

For 4, let’s suppose you stored the Crew data in Objects in the form of Json object, you can then include the Ship info within each corresponding Crew, for instance, sort of like this:

{  "Crew1":{  "Ships":[  "Ship1",  "Ship2"  ]  },  "Crew2":{  "Ships":[  "Ship3",  "Ship4"  ]  },  "Crew3":{  "Ships":[  "Ship5",  "Ship6"  ]  }}

And, again, for the case that each Ship only belongs to One Crew, you may need to add additional client/server logic to make that happen.

For 5, PlayFab offers the Friends feature for you to utilize, however, friendship on PlayFab is a one-way street, sort of like the following system: Player A adds Player B as a friend, Player B must separately add Player A for the friendship to be mutual. Fortunately, there are already some discussions about workaround solutions for a two-way friend system on the forum, here is one of them you may find helpful:

Two-way friend confirmation with Cloud Script

For 6, PlayFab offers the Currencies feature, so each player’s currency info can fall into that part, for other information, you can save them as Player Data/Objects, and, as I mentioned above, it’s suggested that you utilize Entity Objects.

Above are my own personal solutions, you can come up with your own ones once you are familiar with all the PlayFab features.

For your bonus question:

It depends on your own situation, if your game doesn’t need some server-side logic, it’s ok that you use Client APIs solely in clients, however, if your game needs some server-side logic, you may also want to consider using server APIs in server-side .