mozilla-services/android-sync — comment on commit 91987cdd058fcf3752869871022f712e19a0490b
File: src/main/java/org/mozilla/gecko/sync/repositories/android/ClientsDatabaseContentProvider.java line 72
By rnewman:

The `Map` approach gives you GUID-based lookup without iteration. I don't know if we'll ever need that (sending commands? lookup of the type of a client?). If not, the `Set` is fine.