If you have two or more services that need to agree about state, and you have some set of rules that govern what state changes are valid, and you don't want to mess around with any of this "what do we do when we miss and update vs when we get two of the same update" nonsense, and the services aren't in a position to query the same database, then you should really consider a permissioned blockchain. Consensus hard, but it's harder if you're not using tools that understand that what they're going for is consensus.