Juxt hold an occasional conference and this edition was focused on Fintech which isn’t an area that I know really well but have dabbled in a bit.
Opening keynote
Fortunately the opening talk by Fran Bennett of the Ada Lovelace Institute was on AI and draw a parallel between the Post Office/Fujitisu debacle and the current level of credulity around the potential of generative AI. I particularly liked this (paraphrased) quote.
Computer systems operate within existing systems of power
If we choose to believe the myth of infallible machines over fallible humans then injustices like the Horizon scandal will just occur again and again.
Eliminating non-determinism
Allen Rohner of Griffin Bank offered a talk on improving testing systems by taking aim firmly at “flaky” tests and attributing them to non-deterministic and side-effecting behaviour either in the system under test or in the testing code itself.
He used the example of the FoundationDB testing strategy and a focus on invariant behaviour to facilitate automated generative testing. The practical twist he offered on this was Griffin’s use of stateful proxies that can also be part of generated testing to provide something strong than mocks or stubs in integration testing.
I think the key takeaway though was to change the way that you think about unreliable tests and consider changing the system to solve the problem rather than hacking around the tests.
Workflows in service clothing
Phill Barber‘s talk on workflows was one of my favourites of the day. Perhaps because I wasn’t expecting to enjoy it and partly because his argument in favour of workflows and orchestrated workflows (over choreographed events) was persuasive. He also didn’t try to deny the problems there can be with workflows: like only being able to visually design them and then exporting them to source control and never delivering the ability to for non-technical to change the system.
He tackled the key issues of the “workflow black hole effect” head on by putting the workflows inside the service boundaries. This approach also minimises the complexity and rigidity that can come from orchestration as you are talking about a few dedicated flows within a service. The orchestration rules are hidden from the service callers and therefore remain malleable.
He also suggested something interesting in that when a collaborating service becomes too anaemic and the balance of functionality ends up in the workflow side you can eliminate the service entirely and allow the workflow to access the datastore associated with the service. In the example given this essentially eliminated a feature light microservice in his example and instead brought the data ownership into a service with broader responsibilities. I would be interested if the idea would extend to multiple data ownerships but the thought only occurred to me well after the event.
He mentioned nflow as an embeddable (JVM-based) open source workflow engine that allows configuration in code.
Monoliths, monoliths, monoliths!
Everyone was of one mind that you should start each development with a monolith as Vlad Yatsenko, CTO of Revolut, put it, the service should be just one box on the system diagram. No-one was fundamentally against microservices but the preference was clear for “right-sized” services divided by organisation or operational properties and to decompose the monolith into the services rather than trying to jump straight to a distributed system.
Magic versus abstraction
In the questions section of the final talk by Zohor Melamed, Harry Percival asked the question about what the difference was between a great abstraction and the “magic” behaviour that Zohor had railed against in his talk. Again paraphrasing the response:
The difference between magic and a good abstraction is that the abstraction doesn’t shape the solution.
Bad abstractions are like async and await, good abstractions are like Docker which genuinely does not leak the details of the running container.
Conclusion
Thanks to Malcolm and Jon for the invite, it was an interesting line up, even for someone for whom the “buy side” is a mystery.