Founding Data Engineer
London – Hybrid (3 days) - £70,000-£80,000 + meaningful equity
Company
Our client is a London-based, well-funded startup specialising in analytics and predictive ML models. They help mobile apps optimise ad spend by analysing behavioural data and delivering predictive signals for high-value conversions. As the first data engineer, you’ll work directly with the founders to build core data infrastructure that powers real business impact.
Responsibilities
As the founding Data Engineer, you will own the design and implementation of data pipelines and infrastructure, including:
* Build production ETL pipelines processing millions of mobile analytics events from MMPs like AppsFlyer and Adjust
* Engineer features for ML models, including temporal patterns, user behaviour sequences, and campaign attribution
* Ensure data quality via validation, deduplication, schema checks, and defensive programming
* Optimise pandas/Polars pipelines for performance at scale
* Handle messy real-world data: duplicates, nulls, schema drift, and out-of-order events
* Build and orchestrate pipelines using Prefect and monitor BigQuery operations
* Establish CI/CD practices and maintain clean, maintainable code
* Integrate APIs with MMPs and advertising platforms, and collaborate with data scientists to productionise ML models
* Set data quality standards and influence the technical strategy for the platform
Requirements
* 4–6+ years of building production data pipelines with measurable business impact
* Deep expertise in Python, SQL, and pandas, with experience in memory optimisation and vectorisation
* Experience managing messy real-world data and maintaining high data quality standards
* Strong code quality practices (e.g., ruff, mypy, pytest, SQLFluff, pre-commit)
* Right to work in the UK and ability to work 3 days/week from Central London office
* Strong problem-solving skills, attention to detail, and ability to work independently
* Experience with workflow orchestration (Prefect, Airflow, Dagster), cloud data warehouses (BigQuery, Snowflake), or backend Python frameworks (Django, FastAPI) is a plus
Benefits
* 25 days annual leave plus bank holidays
* Meaningful equity options as the first engineering hire
* Flexible working: 3 days/week in London office, remote otherwise
* Learning budget for courses, conferences, and professional development
* Direct founder-adjacent experience with strategic input
* Ownership of core systems from near-scratch with full autonomy
* Immediate impact: your code drives production outcomes and company revenue
* Opportunity to shape engineering culture and grow with the company