Steven Holdsworth
Principal engineer. I build platforms on the BEAM: AI systems, data platforms, and the services around them. Nineteen years in.
Northern Ireland (Remote UK/EU)GitHubhex.pm
Updated August 2026 · cv.json
Experience
Principal Polyglot Software Engineer & Architect, Strategic Engineering · Faria Education Group
- Originated and architected the company's AI platform: versioned, auditable AI operations consumed by every product, multi-provider, with a separate China deployment
- Founded the data platform and the Spotlight analytics product, in production across three AWS regions
- Polyglot delivery alongside the Elixir platforms: a .NET document-processing daemon driven from the BEAM, Ruby in the Rails products and clients for my services, Python for the Airflow/dbt analytics stack and a Django MCP server
- Standing AI strategy, AI Ethics Board and leadership-advisory roles; hands-on technical due diligence for M&A
- Designed and ran an agentic SDLC for production-grade delivery; owned technical hiring for seven years
Director of Engineering (part-time) · Enzai
- Engineering leadership through the early start-up phase of an AI-governance software company (part-time, concurrent with Faria)
- Established data-security controls and engineering processes; led Elixir/AWS systems design and shipped features hands-on
Senior Software Engineer, Processing Platform · Alert Logic
- Architected the ground-up replacement of an Erlang security-processing cluster as serverless Erlang on AWS: BEAMs bootstrapped inside Lambda and kept warm, Kinesis and SQS queueing (2016–17)
Senior Software Engineer, CME Direct · CME Group
- CME Direct trading platform (.NET) and stream-processing/CEP systems for market analysis
- Co-designed a behavioural testing framework
Senior Software Engineer, Services & Mobile Platform · NaviNet
- Mobile platform team for US healthcare: native and web medical applications
- Next-generation medical-insurance transactions and a composite web architecture
- Applied programming-language theory to test automation: designed a grammar for automated testing that testers could grow themselves, defining new words in terms of existing ones, an idea inspired by Guy Steele's 1998 OOPSLA talk, Growing a Language
R&D Lead & Technical Consultant · L&T Infotech, consulting at Citi
- Lead developer on the middle-tier overhaul of an account system with 40,000+ active users, in Citi's Architecture & Technology Division
- Introduced TDD, unit testing and automated regression testing; trained developers; consulted by senior staff on process improvement
Software Consultant (self-employed) · Holdsworth & Co Consultants
- Three financial-sector contracts building high-performance analysis systems and tools for black-box trading systems and algorithmic trading strategies
- A from-concept distributed execution platform scaling computation across a cluster for a private trading fund
Software Developer · Digital Future Solutions
- Architected and built the next-generation 3D UI for a distributed multi-room media-centre product (.NET/WPF)
Associate Software Developer · Autonomy Meridio
- Placement year in the core development division, on legacy and new systems in ASP.NET, Silverlight, WPF and SharePoint, working Agile
- Meridio was acquired by Autonomy in October 2007, mid-placement
- My mentor Stuart had me read Code Complete by Steve McConnell in my first week, what a start to a career in programming. Coding horrors, if you know you know
- A colleague's 2008 LinkedIn recommendation: 'very fast learning and committed developer ... pure pleasure to work with'
Technical Specialist · Ulster Bank (RBS)
- Two-month contract on process automation and compliance for a magnetic-tape system, done in UNIX scripting
Projects
Faria AI platform
- Originated and architected the company's AI platform: versioned, auditable AI operations consumed by every product across OpenAI, Azure, Anthropic, Bedrock and Chinese providers, with a China deployment
- Sole-led the credential-holding AI gateway with byte-stream audit, usage and pricing planes (27 ADRs)
- Red-team evaluation suite and safeguard middleware; 46-operation fleet-wide model migration
spirit_fingers: SimHash for Elixir as a Rust NIF
- Wrote spirit_fingers, an Elixir SimHash library backed by a Rust NIF: kept on hex for seven years, roughly 276× faster than the pure-Elixir alternatives, and the engine inside a production duplicate-detection service
chroxy: pooled headless Chrome over the DevTools protocol
- Wrote chroxy, an Elixir headless-Chrome proxy handing out raw DevTools connections from a supervised browser pool: 266 stars, thirteen hex releases, community contributors
Spotlight school analytics
- Founded the school analytics product on the group's data warehouse: attendance and grades domains, curated report views, in production across three AWS regions
- Conceived and built its dynamic insights: statistical models in the warehouse (sliding-window early-warning scoring with acceleration, month-over-month decline, absence-pattern detection) providing reliable, predictable intelligence over the data, the higher-level layer that drives user insights and the LLM interaction
- Built its AI line end to end: natural-language querying over a semantic layer, then an OTP agent skills system, with answers grounded in pre-computed warehouse figures
MiniPD coaching marketplace
- Founding architect and tech lead: 14-app Elixir umbrella, Stripe Connect payments with a double-entry ledger, video and chat
Account-linking and messaging service
- Sole architect of a platform giving web applications that share a human user but not an auth provider an Apple Handoff-style experience: a user-consented, secure link between accounts and messaging over it; OAuth-style handshake, visibility-timeout messaging, contract-first OpenAPI, property-based tests, full IaC, clients in two languages
ASDLC: an agentic software development lifecycle
- Authored ASDLC, a versioned agentic-SDLC specification with a reference architecture and 59-skill catalogue, and proved it by shipping production-grade systems with it
Faria data platform
- Founded and architected the group's data warehouse: medallion bronze/silver/gold on S3, Athena, Glue and Parquet, per-school isolation by construction, Oban-orchestrated ETL across four external source systems
- Preceded by a prototype I founded and then argued against: embedded BI over a lake, written up as a negative result that set the platform's direction
exile: Spawnfest 2019 winner
- Spawnfest 2019 winner: originated and led a realtime database-as-a-service built in 48 hours
Cherry: a static site generator for hackers
- Wrote Cherry, an Elixir static site generator with typed collections, a thirty-theme contract and portfolio/CV output (this site runs on it)
Coursework near-duplicate detection
- Realised my own 2018 RFC as a service the same year, then rebuilt it in 2023 on my open-source Rust NIF and scaled it to 100 MB files
A Christmas of hex packages
- Wrote and published three Elixir libraries to hex over December 2025: conjure (Anthropic Agent Skills for the BEAM), deep_eval_ex (LLM evaluation, a port of DeepEval) and chatterbex (text-to-speech bindings)
Upstream contributions to Elixir libraries
- Contributions merged upstream into open_api_spex, gen_magic, ex_aws_bedrock, ex_aws_s3 and pow
Performance harness on my own headless-Chrome service
- Sole author of my earliest work at Faria (from November 2017): a latency- and geography-aware performance-recording harness for an exam-systems product, driving real user scenarios over HTTP
- Built on chroxy and chroxy_client (my own open-source headless-Chrome service), a personal library driving employer performance tests (dependency stated, ownership personal)
- A Phoenix front end to run the scenarios and visualise the timings; runs stored in Postgres for regression tracking
codebase-memory-mcp: Elixir support for a C code-intelligence engine
- Contributed Elixir semantic resolution and a nine-defect hardening campaign to DeusData's C code-intelligence MCP engine, validated against a 1,240-file production Phoenix application (impossible call edges 174 to zero)
Data and analytics prototype
- Founded the data-analytics prototype whose negative result set the direction for the platform that followed (2024)
- Proved the ingestion to warehouse to dashboard chain end to end, then argued against shipping it
School-authorisation application
- Founding engineer (October 2018): the scaffold, the first domain model and entity APIs across seven entities, and the releases/Docker/CloudFormation deployment story later imitated in a sibling service
- 2023–24: replaced a document-export bodge with a vendored conversion daemon of my own; built a queue-backed CRM export subsystem (durable database queue, supervised poller)
cherrypicker: named .localhost URLs for local dev servers
- cherrypicker: stable named .localhost URLs for local dev servers, written in Elixir with no Node toolchain and no root CA
Technical hiring programme
- Designed and owned the division's technical assessments for seven years, spanning three role tracks: software engineering, data engineering and full-stack
- Challenges built to reward genuine reasoning: worked examples where the greedy algorithm fails, a round-two "extend your solution" stage, and candidate communication recorded and scored alongside code
- 2025–26: AI-assisted calibration with generated exemplar solutions and agent-drafted, human-curated code reviews
Storeguard: Shopify merchant-health app
- Sole author: a complete embedded Shopify app in eight days (React Router 7, Prisma, BullMQ)
- CI chain from schema generation through lint, types, tests and build to two dependency-audit gates, the production audit zero-tolerance; 57 Playwright specs in about 46 seconds
- A visual end-to-end loop that screenshots every UI state at three breakpoints into a README index, built for AI-assisted review
NHdrHistogram: HdrHistogram ported to .NET
- Ported HdrHistogram to .NET (2013), from the low-latency trading years
A realtime message-relay service
- Sole author of service and client alike: a JWT-scoped pub/sub message relay over Phoenix Channels, the reusable replacement for a Rails product's ageing realtime transport
- A scope/session model so messages fan out only within their scope; authorisation entirely by JWT
- Shipped the service and its JavaScript client together, versioned to production
BeerExpert: an expert system in Elixir
- BeerExpert (2015): an Elixir expert system from my first year on the BEAM, 14 GitHub stars
ReactiveReact: an RxJS and React playground
- ReactiveReact (2014): an RxJS and React playground from the Rx years