Spencer Clark

About

I've spent nearly thirty years building software for UK financial services — wealth management platforms mostly, in .NET and Postgres, in domains where the regulator eventually asks what you did and why.

Long enough to have watched several systems age. That turns out to be the part that interests me most: not what a system does on the day it ships, but what it does five years later when the people who built it have gone and the assumptions they never wrote down are still load-bearing.

I co-founded Wealth Dynamix in 2012 and spent five years as CTO while it grew to around ninety people. Later I started Portemis, which was acquired, and returned to Wealth Dynamix as senior architect looking after the unglamorous half — architecture, Azure, DevOps, reliability, the things that decide whether a platform is still maintainable in a decade.

Since July 2026 I've been building Cairn, an evidence layer for regulated work. It records what was done, why, and when, so a team can show the process they followed months or years later. Reviews, checks, approvals, exceptions — work where the record matters more than the artefact.

What this site is

Write-ups of things I've measured.

Here I learn by building something small and instrumenting it, and the measurements are usually more interesting than whatever I expected to find. Several of the posts here exist because a cheap test overturned something I was confident about. Those are the ones worth writing down.

I try to publish the wrong turns as well as the conclusions. A clean narrative that arrives at the right answer first time is a less useful artefact than one that shows which hypotheses got eliminated and how — and it's usually not what happened.

Working principles, for what they're worth: prefer the smaller option, prefer boring explicit code to premature abstraction, and make deviation permitted but never silent.

Elsewhere

I'm happy to hear from people working in compliance, operations, oversight, regulated financial services, or anywhere the process record matters. Equally happy to talk about anything on this site.