I usually preach that a big blob of mutable state in the middle of your system (the db) is the problem, and events are the solution, and this seems like its most obvious case.
All your problems start when you try to modify your current state representation in response to hearing the USER_ADDED or USER_BLOCKED events. Just don't. Leave them as events. Any time you have a new stupid edge case (double send, out-of-order, add-then-delete-then-add), this becomes one new unit test, where you can soberly decide what it means, and update your read path to understand it.
If you bake the nonsense into the current db state every time a new event arrives, your first step in any debug or reasoning scenario is to unbake it: what events led to this mess? If you don't throw away the events, your debugging is done for you.
Comments
I usually preach that a big blob of mutable state in the middle of your system (the db) is the problem, and events are the solution, and this seems like its most obvious case.
All your problems start when you try to modify your current state representation in response to hearing the USER_ADDED or USER_BLOCKED events. Just don't. Leave them as events. Any time you have a new stupid edge case (double send, out-of-order, add-then-delete-then-add), this becomes one new unit test, where you can soberly decide what it means, and update your read path to understand it.
If you bake the nonsense into the current db state every time a new event arrives, your first step in any debug or reasoning scenario is to unbake it: what events led to this mess? If you don't throw away the events, your debugging is done for you.