[kthejoker2]

"Single source of truth" is usually seen in data warehousing /BI world, where you have multiple source systems (say, a CRM and a ordering system) or reporting systems and you want them to agree when yous ask, "how many repeat customers did we have last month?"

On the app dev side, where you frequently have more writes than reads, and transactional guarantees (e.g. not allowing a bank transfer if there's no money in the account) ... what you want is eventual consistency, or some form of pessimism built in to your state maangement.

So not really "single source of truth" so much as "single way of reconciling the consequences of distributed event processing."