Consistency

The impossibility of exactly-once delivery

The impossibility of exactly-once delivery

Savvas Kleanthous
We all know the joke about distributed systems right? There are only two hard problems in distributed systems: 2. Exactly-once delivery 1. Guaranteed order of messages 2. Exactly-once delivery — Mathias Verraes (@mathiasverraes) August 14, 2015 (btw you should go follow Mathias if you don’t already) 1 Exactly-once delivery defined First of all: Exactly-once delivery guarantee is the guarantee that a message can be delivered to a recipient once, and only once.
The two generals problem and the impossibility of consensus

The two generals problem and the impossibility of consensus

Savvas Kleanthous
This is the second blog post in a short series about Consistency I love the two generals problem. I am mesmerized by its simplicity and impossibility. And I believe nothing has shaped my professional life more than this problem. Back in 2008 I had not yet worked with any major distributed systems, and most of my work was with systems which involved heavy aspects of custom electronics; one could say I was into IoT before IoT was a thing.
A primer and a rant about eventual consistency

A primer and a rant about eventual consistency

Savvas Kleanthous
This is the first blog in a short series about Consistency When I decided to start my blog again, I created a poll about what should I write first. The reason was that I have gathered material about 2-3 subjects which I liked and wanted to speak about, but I wasn’t sure which one to start with. More people voted than I expected, but the decision was a tie between what different types of events would be helpful to recognise in an Event Sourced system, and Distributed consistency.