Product · MarTech · Engineering — Berlin

Think it. Build it.
Ship it.

I design and build digital platforms end to end — B2B self-service products, data platforms and AI-supported workflows — and lead the teams that ship them.

Discuss a project → See experience
John Harder
Available now · full time
Remote & Berlin
Strategy → Code
Owned end to end
Web · Mobile · Data
Designed & built
10 years
e-commerce, AdTech & MarTech · Product + Architecture
Remote-first
Berlin · across the EU
Expertise

What I bring

Product leadership, marketing technology and hands-on engineering — end to end. I can own the strategy and the roadmap, and build the platform that delivers it.

01

Product Leadership & Strategy

  • Product vision, strategy & roadmaps
  • Discovery, requirements & scoping
  • KPIs, metrics & data-driven decisions
  • Leading product organisations of 20–25 people
02

Solutions Architecture

  • End-to-end technical concepts: cloud, frontend, integration
  • API, batch and event-based system integration
  • Migrations and legacy replacement without downtime
03

Data Platforms & Reporting

  • Ingestion, transformation & delivery pipelines
  • Warehousing with BigQuery & Snowflake, orchestration with Airflow
  • Dashboards, KPIs & client-facing reporting
04

Marketing & Ad Technology

  • Programmatic advertising, RTB, DSP / DMP / CDP
  • Retail media & self-service ad products
  • Tracking, attribution & data protection
05

Software & Delivery

  • Web & mobile apps (React, TypeScript, Capacitor for iOS & Android)
  • Backends & APIs with Node.js and Python
  • Infrastructure as code with Terraform on GCP & AWS
06

AI & Automation

  • LLM services in production: classification, semantic matching, generation
  • AI-supported research, analysis & content pipelines
  • LLM-assisted development from prototype to production
Tools & Stack

From product tooling to the tech stack

The platforms, tools and languages I work with across product, marketing technology, data and engineering.

Product & Delivery

Roadmaps · KPI frameworks
Discovery · Build-vs-buy
Cross-team delivery

Marketing & Ad Tech

Programmatic · RTB
Xandr DSP · Google Ad Manager
Permutive · Exactag

Languages & Web

Python · TypeScript
JavaScript · SQL
Node.js · React · Capacitor

Data & BI

BigQuery · Snowflake · Airflow
PostgreSQL · MySQL
Looker Studio · Power BI

Cloud & Infrastructure

GCP · AWS · Cloud Run
Pub/Sub · Serverless
Containers · Terraform

AI & Automation

LLM services · Semantic matching
Contextual models · Text-to-speech
Data pipelines

Experience

10 years in product, platforms and AdTech

Ten years of product leadership and hands-on delivery across e-commerce and advertising technology. Full history on LinkedIn.

2024 — now
nexxtep
Berlin / Hamburg

Principal Product Manager

Lead B2B self-service and data platforms for a leading e-commerce marketplace with several thousand partners — concept, architecture and delivery across multiple engineering teams.

B2B platformsData platformsArchitectureDelivery
2023 — 2024
BurdaForward
Berlin / München

Technical Product Lead — Contextual Data

Led contextual data-science models and the pipelines behind them with a team of nine engineers and data scientists.

Data sciencePipelines
2021 — 2023
Otto
Berlin / Hamburg

Lead Product Manager — MarTech

Product direction, roadmap and KPIs for OTTO's retail media products across a 20–25-person engineering and data organisation.

Product strategyRoadmapsRetail media
2019 — 2021
Otto
Berlin / Hamburg

Initiator & Product Manager — OTTO Display Network

Initiated and built OTTO's proprietary cloud advertising infrastructure: first-party data management, ad tracking, reporting and self-booking frontends for retailers.

First-party dataAd trackingSelf-service
2016 — 2019
Otto
Hamburg

Display Advertising — from working student to Tools & Technology Manager

Ran and developed the display ad stack: DSP and ad server setup, API integrations, retargeting.

DSPAd serverAPIs

Education — M.Sc. Media Informatics, Lübeck (thesis: Dynamic Creative Optimization in programmatic advertising) · B.Sc. Media Engineering, Hamburg.

Selected cases

Projects with concrete deliverables

Starting point, my contribution, outcome — what typical collaboration looks like.

01
Platform · Product lead

B2B self-service platform

Starting point

A marketplace with several thousand partners needed a self-service platform to plan, book and optimise services end to end — goals, budgets, audiences, content, reporting — replacing a legacy platform and manual processes.

Contribution

Product lead for concept and delivery. Owned the technical concept: cloud platform, frontend stack, and the integration architecture to internal and external systems (API vs. batch, frequencies, contracts). Led two engineering teams directly, steered four to five further platform teams.

Outcome

Live in production. Legacy platform replaced and legacy services decommissioned.

02
Data engineering

Data platform for internal and client reporting

Starting point

Business data spread across many source systems, no single reliable basis for internal reporting and client reports.

Contribution

Built the platform hands-on with two engineers: ingestion, transformation and delivery. BigQuery, Snowflake, Airflow, Cloud Run services and jobs, Pub/Sub, fully provisioned with Terraform.

Outcome

Running in production; feeds internal reports and client-facing reporting.

03
Architecture & migration

System integration and migration

Starting point

An auction and bidding system, a data layer and a legacy self-service platform had to move onto a new stack without interrupting live product flows.

Contribution

Owned the migration architecture and sequencing; led the integration of the bidding system, the data migration into product flows and the replacement of the legacy platform.

Outcome

Migration completed; legacy services switched off.

04
AI in production

LLM-based content classification and matching

Starting point

Large volumes of unstructured content had to be classified and matched to business customers to drive automated content generation inside a self-service product.

Contribution

Designed and implemented LLM-based classification (metadata), semantic content-to-customer matching logic and the resulting generation flow.

Outcome

In production inside the self-service platform.

05
Scraping, enrichment & automation

Repeatable data processes instead of manual work

Starting point

Information from external sources needed to be collected and processed regularly.

Contribution

Scraping / API import processes, data validation, transformation and handover to reporting & product components.

Outcome

Less manual work, better data availability and repeatable processes.

06
Own product · iOS & Android

Red Thread: Discover Home

Starting point

Narrative city tours as a mobile product — from idea to app stores, with no existing codebase or team.

Contribution

Full technical and architectural ownership: cloud strategy, user management, API and microservices, Android and iOS apps with Capacitor, infrastructure as code with Terraform. LLM services that generate tours from location data and research, with text-to-speech narration. A separate voucher service for third-party distribution.

Outcome

Live on the App Store and Google Play since July 2026. Distributed through Viator; Google Things to Do in preparation. → redthread.world

References

Where I build & lead

Beyond client work — a shipped product and a company I'm directly involved in.

Reference · iOS & Android app

Red Thread: Discover Home

Narrative city walking tours — part documentary, part podcast — generated by LLM services and narrated with text-to-speech. Own concept, architecture and code.

App Store ↗ Google Play ↗ redthread.world ↗
Co-founder & Managing Director

Voltaire.Vision

A company I co-lead as managing director.

voltaire.vision ↗
How I work

Pragmatic, hands-on, outcome-driven

Don't talk about solutions forever — build a first working version fast, learn from it and improve it iteratively.

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Contact

Let's build something you can actually use.

Got a clearly scoped project with a concrete outcome? Tell me briefly what it's about — I'll come back with an honest take on feasibility, scope and effort.

Also open to senior product leadership roles — Berlin or remote.

info@johnharder.com → LinkedIn