how do you guarantee atomicity across module boundaries? The more fundamental answer is: It depends upon questions such as whether the system seeks to exhibit

how do you guarantee atomicity across module boundaries? The more fundamental answer is: It depends upon questions such as whether the system seeks to exhibit parallel processing properties or not, and the application-specific data generation/processing/storage/retrieval/consistency goals. The short answer is: Ideally you don't, because architecturally you are likely creating a monster. The longer answer is that in the case that it is justified (and such cases do exist) you would generally either use a reference to a transaction (potentially knowing that it may be out of date and having a planned strategy for eventual consistency carefully limiting the effect of such to a non-critical scope), or eat the latency overheads and use an established algorithm - see https://en.wikipedia.org/wiki/Atomic_operation https://en.wikipedia.org/wiki/Atomic_operation https://en.wikipedia.org/wiki/Consensus_(computer_science) https://en.wikipedia.org/wiki/Consensus_(computer_science) and https://en.wikipedia.org/wiki/Consistency_model https://en.wikipedia.org/wiki/Consistency_model - which for most of us simply means 'choose your database/network replication layer carefully'.