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+# Tradeoffs/Design Decisions
+* Key-Value store instead of relational
+    * `+` Schemaless, easier to evolve
+    * `-` No need to fully normalize the data in order to make it queriable. And without full normalization SQL is not really useful and bad performance wise. 
+    * `-` We need to maintain our own indexes
+
+* Individual store per resource
+    * Storage format defined by resource individually
+        * `-` Each resource needs to define it's own schema
+        * `+` Resources can adjust storage format to map well on what it has to synchronize
+        * `+` Synchronization state can directly be embedded into messages
+    * `+` Individual resources could switch to another store technology
+    * `+` Easier maintenance
+    * `+` Resource is only responsible for it's own store and doesn't accidentaly break another resources store
+    * `-` Inter`-`resource moves are both more complicated and more expensive from a client perspective
+    * `+` Inter`-`resource moves become simple additions and removals from a resource perspective
+    * `-` No system`-`wide unique id per message (only resource/id tuple identifies a message uniquely) 
+    * `+` Stores can work fully concurrently (also for writing)
+
+* Indexes defined and maintained by resources
+    * `-` Relational queries accross resources are expensive (depending on the query perhaps not even feasible)
+    * `-` Each resource needs to define it's own set of indexes
+    * `+` Flexible design as it allows to change indexes on a per resource level
+    * `+` Indexes can be optimized towards resources main usecases
+    * `+` Indexes can be shared with the source (IMAP serverside threading)
+
+* Shared domain types as common interface for client applications
+    * `-` yet another abstraction layer that requires translation to other layers and maintenance
+    * `+` decoupling of domain logic from data access
+    * `+` allows to evolve types according to needs (not coupled to specific application domain types)
+
+# Risks
+* key-value store does not perform with large amounts of data
+* query performance is not sufficient
+* turnaround time for modifications is too high to feel responsive
+* design turns out similarly complex as Akonadi