Versioning in an Event Sourced System - TLDR

This is an extremely short version of the excellent writing by Greg Young on versioning in Event Sourcing. It can also be applied in other systems as well.
Most of what is written here - my own interpretation of the original book or sometimes quoted as-is and as such, all credit goes to Greg Young for this. I only added minor notes and only extended on the GDPR erasure a touch.

I want to write it in a "bullet point" style for myself as a reminder and a short summary. Versioning techniques Basic Versioning A new version of an event must be convertible from the old version of the event.
If not, it is not a new version of the event but rather a new event.Event.version (version on every event)InventoryItemDeactivated, InventoryItemDeactivated_v2, InventoryItemDeactivated_v17 (class for every version) Thus, any InventoryItemDeactivated_vNNN can be converted to InventoryItemDeactivated_CURRENT and previous versions are never “visible” from app perspective
Adding new version of an …

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