[ZenPsycho]

I'm just an ignorant nobody, but why would you split a microservice off along a facet that would require transaction and referential integraty? Wouldn't you want to pick off pieces that could be truly independent and not need to care about transactions or referential integrity? otherwise, what problem are you actually solving by splitting the piece off?

[quizotic]

If you never need to coordinate two or more microservices, then sure. But that means you're dealing with a monolith. In the original article, you could combine Orders and Users into a single microservice. That would resolve all the issues that are raised ... except that you might want reference the Users in a different context. At that point, you either have to split Users into their own microservice, or duplicate the User information. Either way, you're backed into consistency issues.

Part of the promise of microservice is that they're small modular independent components that you can connect and combine into higher-level services.

If you need to read information and write information to two or more microservices, then you have transaction issues. If you need to relate information across two microservices, you have reference integrity issues. Just comes with the terrain.

[scarejunba]

Well, that isn’t a problem when you don’t care about the situation right now. For instance, let’s say you have VideoDescription, VideoSubtitling, and VideoContent as different microservices serving a description, the subtitles, and a handle to a list of content chunks. You need these things to line up (in that you may want all this for a single video). If VideoCentral says that you no longer have a movie it doesn’t matter. You can still serve video descriptions, subtitles, and content chunks until your view of the world changes. No big deal. If it is a big deal, then maybe the model doesn’t fit your problem. But for lots of software it really doesn’t matter. You don’t need instant consistency. If it’s consistent at some point that will do.

At no point will the writes insta-percolate. Instead you’ll push the writes into an event queue, they’ll execute eventually, and when the consuming services eventually update they’ll read the new result.

[TeMPOraL]

> Part of the promise of microservice is that they're small modular independent components that you can connect and combine into higher-level services.

Sounds to me that the marketing copy for microservices is missing a crucial observation: the reason independent components aren't hard to work with in regular software is partly because everything runs single-threaded, or if you end up multithreading, the response is predictable and near real-time, the environment is reliable and under your control. These conditions essentially mask transactional and integrity issues, which only become apparent as you scale to multiple machines connected over a network.