Am I dumb or is this basically the binlog of your database but without the tooling to let you do efficient querying?
Like I get the "message bus" architecture when you have a bunch of services emitting events and consumers for differing purposes but I don't think I would feel comfortable using it for state tracking. Especially when it seems really hard to enforce a schema / do migrations. CQRS also makes sense for this but only when it functions as a WAL and isn't meant to be stored forever but persisted by everyone who's interested in it and then eventually discarded.
> Especially when it seems really hard to enforce a schema / do migrations
Enforcing the schema isn't too hard ime. But every migration needs to be bi-directionally compatible. That's likely what they meant with "you need an architect and can't make major changes later on"
It's the same issue you've had with nosql, even though you technically do have a schema
Yes, if version 1.3 of Command handler X was the active version when an event happened, then it needs to be replayed with that version, even if you’re now on v4.5.
> Am I dumb or is this basically the binlog of your database but without the tooling to let you do efficient querying?
Yes, and I honestly think a traditional database that exposed this stuff would be a winner (but I guess it's too hard, and meanwhile event-sourcing frameworks are building better alternatives). Separating the low-level part from the high-level part that does things like indexing and querying has a lot of advantages: you decouple data storage from validation so you can have validated data without having to drop invalid data on the floor, you decouple index updates from data writes so your scaling problems get way simpler, you can get sensible happens-before semantics without needing transactions that can deadlock and all the crazy stuff that traditional databases do (secret MVCC implementations while the database goes out of its way to present an illusion of a single "current" version of the data, snapshotting that you can't access directly, ...).
For events you include a version. When you're only adding properties to the event or removing properties (assuming you defensively write the projectors), no need for a new version, but if you're creating a breaking change in event schema, you'd increment the version for the event and update your projector to handle each version. It's simpler than you'd think.
Like I get the "message bus" architecture when you have a bunch of services emitting events and consumers for differing purposes but I don't think I would feel comfortable using it for state tracking. Especially when it seems really hard to enforce a schema / do migrations. CQRS also makes sense for this but only when it functions as a WAL and isn't meant to be stored forever but persisted by everyone who's interested in it and then eventually discarded.