Designing Webhook Delivery You Can Defend in an Audit
Retries, idempotency keys, and dead letters as an evidence problem, how to build Rails webhook delivery that survives a HIPAA audit, not just a happy-path integration test.
I build and ship complete products on a fixed scope.
I'm Wagner Matos, a UK based senior product engineer. I take software from idea to production, AI accelerated, senior led, with a track record in healthcare, pharma, and other regulated environments. Remote across the UK, US, and Europe.
One senior engineer, accountable end to end. Modern AI tooling does the heavy lifting; fifteen years of shipping by hand - for Johnson & Johnson, GSK, Babbel, Carwow, Citizens Advice - supply the judgment. You get working software at a fixed price, not a burn rate.
How it works
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Step 1
One week: your idea becomes a spec, an architecture, and a fixed quote.
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Step 2
Fixed-scope build
I build the agreed product with visible progress at every milestone, no surprises.
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Step 3
Launch & support
Deployed, documented, and supported after it goes live.
Not a build? I also take contract engagements and fractional support. More on the services page.
What clients say
When we hand Wagner a build with a hard deadline - a congress opening, a live event - it ships. Complete, working, on the floor when the doors open.
Wagner was enjoyable to work with. He was able to quickly get up to speed, immediately wrapping his brain around problems and shipping clear code to fix them.
Wagner handled our blog migration end to end including migrating all content, URLs and redirects for SEO, and a custom Cloudflare Worker. All documented and deployed with zero drama.
Building for environments you don't control
Hospital networks that allow nothing in, devices in the field you cannot brick, conformance requirements you cannot negotiate, and stakeholders who need it in plain English. What engineering discipline looks like when the environment sets the rules. From a clinical alerting platform used by NHS trusts and a fielded detection product.
The event floor stack: building interactive experiences that survive a congress
If you run production at an event agency, you know the shape of this problem. The client has bought an interactive idea for their stand. A touchscreen, a photo experience, some kind of engagement measurement. You have sold it, you have a date, and...
Anatomy of a fixed-scope build
"Fixed scope, fixed price" sounds like a line from a brochure until you watch one run from start to finish. So here is one. Last September I built EventScope for Johnson & Johnson Medical: an engagement analytics platform that ran across their...
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Recent Work
Johnson & Johnson
During the ECP Congress 2025, Johnson & Johnson needed a way to bring their precision medicine story to life on the exhibition floor. Healthcare professionals would be passing through quickly, the experience had to attract, educate, and track engagement, all without depending on venue Wi-Fi or cloud infrastructure.
Confidential (healthcare)
I built a serverless webhook service that delivers real-time conversation events to each NHS trust's own systems, handling encryption, authentication, concurrent delivery, and automatic retries.
Johnson & Johnson
For Johnson & Johnson Medical Affairs at a major international medical congress in 2025, I built an interactive presentation kiosk that works with no network at all, and still hands the team a full picture of what visitors looked at, for how long, and how far they got. The fourth build for the same client team, across three congresses.
Johnson & Johnson
During the European Academy of Dermatology and Venereology (EADV) 2025 Conference, Johnson & Johnson Medical aimed to better understand how healthcare professionals interacted with their multi-zone exhibition booth. Traditional tracking methods lacked real-time visibility and were often dependent on unreliable event Wi-Fi and cloud connectivity.