About

Hello, I'm Mira.

I started out writing PHP for a local newspaper and have since worked in fintech, healthcare and developer tooling, at companies from four people to four thousand.

These days I work independently with a small number of clients at a time. Most engagements involve a system that has to be dependable: money moving between accounts, patients booking appointments, researchers trusting their data.

I care about clear writing as much as clear code. Every engagement ends with documentation, a recorded walkthrough and a team that is confident running what we built together.

Outside work I maintain a couple of small open-source tools, mentor career changers through a local bootcamp and spend too much time cycling up hills around Bristol.

Placeholder portrait of Mira Castell

Experience

Where I've worked

  1. 2022 to now

    Independent software engineer

    Mira Castell Engineering Ltd

    Product, platform and audit engagements for fintech, healthcare and SaaS teams.

  2. 2018 to 2022

    Staff engineer

    Northgate Labs

    Led the payments platform team and introduced the company's design-review process.

  3. 2015 to 2018

    Senior engineer

    Kestrel Insurance

    Moved the quote engine from a monolith to services and built the internal developer portal.

  4. 2013 to 2015

    Web developer

    Avon Courier Digital

    Built the newsroom's publishing tools and the paper's first responsive website.

Toolbox

What I work with

Tools change; the habits behind them don't. These are the ones I reach for most often.

Languages

  • TypeScript
  • Go
  • SQL
  • Python
  • Bash

Front end

  • Astro
  • React
  • Web Components
  • CSS
  • Playwright

Back end and data

  • Node.js
  • PostgreSQL
  • Kafka
  • Redis
  • ClickHouse

Infrastructure

  • AWS
  • Google Cloud
  • Terraform
  • Docker
  • OpenTelemetry

Principles

How I work

  1. 01

    Small, reversible steps

    Feature flags, shadow modes and gradual roll-outs. Big-bang releases are where projects go to die.

  2. 02

    Write it down

    Design notes, decision records and runbooks are part of the work, not an afterthought.

  3. 03

    Measure first

    Performance, reliability and cost are measured before they're optimised.

  4. 04

    Leave a team behind

    Success is your engineers owning the system confidently after I've gone.

Available for new projects from January 2027

Have a project in mind?

Tell me what you're building and where you're stuck. I'll reply within two working days with honest next steps, even if I'm not the right fit.