As I understant it: Consider you have a database where you store the account balance. If you want to update the account balance you might update the row for t

As I understant it: Consider you have a database where you store the account balance. If you want to update the account balance you might update the row for that customer, e.g. tblAccounts ------------ | AccountHolderId | AccountBalance | update tblAccounts set AccountBalance = @NewAccountBalance; In an EventSource database instead you wouldn't update the AccountBalance column. You would store something like: AccountEvents | AccountHolderId | AccountBalance + 100.00 | AccountHolderId | AccountBalance + 150.00 | AccountHolderId | AccountBalance - 80.00 Then ifyou wnat o get the current balance you can just take the opening balance and add 100, add 150 and subtract 80. Periodically you need to collapse these as querying for the balance could end up requiring going through a large log of events. So you snapshot at some point in time. So assuming an opening balance of zero, we could snapshot the above to 170.00. It feels like you get auditing / logging of all changes out of the box, also if you are working in functional programming or a system where you constrain side / mutability as much as possible you sort of eliminate your db as a giant mutable object. But you also get the downsides this article talked about.