Szymon Pobiega

Szymon Pobiega

Szymon works an engineer at Particular Software, the makers of NServiceBus. His main areas of expertise are Domain-Driven Design and asynchronous messaging. He is especially interested in the intersection of these two topics -- in the patterns and tools for ensuring all messages are processed exactly once and in the correct order.

Szymon is a co-author of https://exactly-once.github.io/, a site dedicated to correct message processing.

Montreal 2020 sessions

Event-driven microservices: what can go wrong?

English session - Intermediate

In the classic paper Data on the Outside versus Data on the Inside Pat Helland argued that data within a service boundary should be treated differently than data residing outside of it.

Here, I shall argue that the same applies to messages. Inside a service boundary messages are tightly coupled to the corresponding data manipulations. Outside, the world is much more hostile and less predictable and communication strategy needs to be adequate.

Excuse me, my bill does not match my order

English session - Intermediate

In a distributed system messages sometimes get lost or duplicated. That's a fact of life. It is really hard to execute business logic that assumes one trigger equals one outcome when a trigger can be lost or fire twice.

One way of dealing with the problem is taking advantage of natural idempotency of some operations, e.g. adding element to a set. But let's face it, most code is more complex than that. Join me an explore some alternatives.