For a few projects we make use of the Event Engine by prooph software which is a biased - in a good way(tm) - way of quickly building event sourced applications. While building a user registration context, I was stuck a bit how and where to properly hash the password for the user. I could have done it in the init() method of the command, that way I would have made sure that the cleartext password is not "visible" anywhere in the application code. In the end, I decided to make use of a provider class. The return value of the provider will be passed to the specified aggregate method and allows me to pass it to the respective event.
In a recent project, we make use of the Event Engine which is an Event Sourcing framework for PHP helping you to rapidly develop event sourced applications. Since parts of the exposed API by the Event Engine should be access proteced, we decided to use OAuth2 for access delegation. That way each route exposed by the Event engine application can be marked as "protected" if needed.
While working on this prooph components powered API, I realized it would make sense for our mobile client to know when data changed on the server-side without constantly pulling all data from the API and comparing it locally. In a "traditional" application I would have used a checksum mechanism - e.g. creating a checksum of all the data in the datastore - but with an event sourced application this is no longer needed as we can simply rely on the timestamp of the last event happened to know if things have changed.