Heiko Falkenstein
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Tracking & Data Infrastructure · Server-side GTM · GA4 · Meta CAPI
Sebastian
Kawa.
I rebuild tracking and data infrastructure for D2C and e-commerce brands — server-side, first-party, attribution that actually works. A decade of senior engineering in production e-commerce. Based near Cologne, remote preferred.
Hire me
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Replies within 24h · Mon — Fri
About
This is me.
Hi — I'm Sebastian. For the last decade I've been senior engineer on a small in-house team at a leading German D2C food brand, end-to-end ownership of the e-commerce platform and the tracking stack underneath it.
My focus is the part of the stack that quietly costs the most when it breaks: tracking and data infrastructure. Server-side GTM, GA4, Meta Conversions API, first-party data layers, conversion deduplication. When attribution is broken, ad spend goes blind, A/B tests lie, and growth decisions get made on bad data. I rebuild that foundation.
Beyond tracking, I bring full-stack depth across Magento 2, Laravel, REST APIs, and integrations — useful when "the tracking problem" turns out to be "the platform problem," which it often does. Currently open to new engagements. Remote preferred. Working in German and English.
Stack
The stack.
Tracking & Data
Server-side GTM
GA4
Meta CAPI
Data Layer
Deduplication
A/B Testing
Backend
PHP 8
Laravel
Magento 2
REST APIs
Data
MySQL
Redis
Query tuning
Infra & Ops
Docker
Webhooks
Release mgmt
Integrations
Adyen
DHL
Algolia
n8n
Frontend
JavaScript
HTML / CSS
Experience
A decade in place.
Just Spices
Senior Software Engineer
Nov 2024 — Present
Just Spices
Web Developer · Fullstack
Oct 2015 — Jan 2025
Rhine-Waal University
B.Sc. Media Informatics
Graduated 2017
Selected work · 2015 — 2025
Track record.
_01
Magento 1 → 2 Migration
_02
Adyen Payment Gateway
_03
Referral & Loyalty
_04
A/B Testing Framework
_05
DHL Shipping Pipeline
_06
Algolia Product Search
_07
n8n Automation
_08
GA4 Tracking
W.01 · Migration
Magento 1 → 2 Migration
End-to-end platform migration. Data migration, module rewrites, theme rebuild, phased deploy — store stayed live throughout.
W.02 · Payments
Adyen Payment Gateway
Checkout and back-office integration. Multiple methods, multi-currency, 3DS compliance, hardened webhooks.
W.03 · Retention
Referral & Loyalty
Referral engine inside the retention programme. Tracking, rewards, fraud controls, reporting.
W.04 · Experimentation
A/B Testing Framework
Controlled tests on conversion, UX and pricing with clean analytics attribution.
W.05 · Logistics
DHL Shipping Pipeline
Order management → DHL. Labels, tracking, returns — a resilient automated pipeline.
W.06 · Search
Algolia Product Search
Indexing, relevance, facets, iterative tuning — to lift conversion from search.
W.07 · Automation
n8n Automation
Internal tools, CRM and marketing linked through reliable, observable workflows.
W.08 · Analytics
GA4 Tracking
Event taxonomy, enhanced e-commerce measurement, server-side tagging.
Freelance · Currently accepting new projects
Client work.
Free site & tracking scan · Any e-commerce store
See what your site
See what your site
is leaking.
Send me your domain and I'll come back within 48 hours with a one-page snapshot: Lighthouse performance and Core Web Vitals, every tracking pixel firing on the page, your data-layer state, your third-party tag load, and how your consent banner behaves. No credentials needed, no pitch unless you ask.
If you want me to dig into the parts I can't see from the outside — deduplication, server-side setup, attribution — that's a paid engagement on top.
- Lighthouse performance + Core Web Vitals (mobile + desktop)
- Pixel inventory: which tags fire, on which events
- Data-layer presence, event coverage, sGTM detection
- Third-party tag count and load-time impact
- Consent-banner behaviour: pre vs post-consent