Maksymilian Maciejewski — Senior Data Analyst & BI Engineer. SQL pipelines, ETL and dashboards that C-level, operations and marketing teams actually use, owned end to end from stakeholder requirements to production.
01 — About
I'm a senior data analyst and BI engineer with 10+ years of experience building SQL pipelines, ETL processes and dashboards used by C-level, operations and marketing teams. Since 2022 I've worked as an independent B2B contractor for an online travel platform serving millions of users, a smart-parking operator, an e-signature fintech and an InsurTech advisory firm, owning the full chain from stakeholder requirements through BigQuery/Dataform, Athena/Trino and PostgreSQL pipelines to Tableau, Power BI, Looker Studio and QuickSight dashboards. Before that, I spent nearly ten years in Widex's EMEA manufacturing operations, rising to department manager, leading a team of four engineers and automating production reporting with SQL Server, SSIS and Power BI.
I turn business questions into data models and reports people actually use, automate recurring manual reporting, and own delivery end to end, from requirements with stakeholders to production.
The most exciting thing I've built
The BigQuery ETL layer in Dataform, versioned in GitHub, feeding the semantic layer and the Tableau and Looker Studio dashboards that C-level used for decision-making at an online travel platform serving millions of users.
Recent engagements
E-signature / fintech
Senior Data Analyst (Freelance)
Smart parking / mobility
Business Analyst (Freelance)
Online travel platform
Business Intelligence Engineer (Freelance)
Earlier career
Widex, hearing-aid manufacturing (EMEA)
From production technical support to department manager, leading a team of four engineers
Certifications
Working languages
02 — Services
I cover the full value chain: warehouse models and pipelines, business logic and metric definitions, dashboards that executives and operations teams actually use, and automation that removes repetitive manual reporting. Solutions are built in code, versioned and documented, so the client keeps full ownership and independence.
Layered warehouse models (staging, intermediate, marts, semantic layer) with tests, documentation and version control. A clear grain, consistent metric definitions and repeatable recalculation instead of logic scattered across reports.
Ingestion and transformation processes that replace manual exports and spreadsheet consolidation. Scheduled, monitored, and designed so that errors are immediately visible.
Dashboards for executives, finance, operations and marketing, designed around the decisions they support. KPI design, financial and revenue reporting, and self-service models for business users.
Moving reporting between platforms or to the cloud without losing trust in the data: report inventory, metric reconciliation, both solutions running in parallel, and a controlled switchover.
GA4 event tracking and KPI modeling, advertising and campaign data, customer behavior and conversion funnel analysis, and time-to-event (survival) analysis, for example time to first login or activation.
Process analysis based on Lean and Kaizen, process modeling in BPMN, production metrics and MES. Ten years in EMEA manufacturing operations, including leading a team of engineers.
Practical use of AI where it shortens delivery or removes manual work: AI-assisted pipeline development, LLM steps in automated workflows, and integration of AI tools with existing data sources.
Assessment of the existing data environment (models, pipelines, reporting, cost) with a prioritized improvement plan; SQL and BI training for business users; documentation and an orderly handover to internal teams.
Ways to work
Scoped project
A concrete deliverable (pipeline, data model, dashboard set, migration) with agreed scope, acceptance criteria and handover.
Ongoing B2B collaboration
A senior analyst or analytics engineer working continuously inside the client's or partner's team, part-time or full-time.
Audit and roadmap
A short review of the current data and reporting environment, ending in written findings and a prioritized action plan.
Skills development and handover
Training, documentation and support so the internal team can maintain and extend the solution on its own.
How I work
Business question first
Every model and dashboard starts from the decision it supports and from metric definitions agreed with stakeholders.
Everything in code
Transformations, tests and definitions are versioned in the client's repository, with no logic hidden in a single report or a private file.
The result belongs to the client
Work is done on the client's infrastructure and accounts; documentation and handover are part of the scope, not an add-on.
Direct communication
Risks, data quality issues and trade-offs are raised early and in writing, together with a recommended solution.
03 — Selected work
Sector descriptions only. Client names can be shared on request, subject to confidentiality.
01 — Online travel
Self-service Tableau and Looker Studio dashboards for the executive team of a platform serving millions of users. ETL in BigQuery built with Dataform and versioned in GitHub. App and web KPIs, and marketing insight extended through GA4 event tracking.
Role
BI Engineer
Stack
BigQuery · Dataform
02 — Smart parking / mobility
Dashboards in QuickSight and Tableau for operations and marketing. Analysis of GA4 data, Facebook Ads and reservation-system logs to understand customer behavior and campaign performance.
Role
Business Analyst
Stack
Athena · Trino
03 — Fintech / e-signature
Looker Studio reporting for executives, operations and marketing. ETL in KNIME on PostgreSQL (Azure). Financial and revenue reporting, analytics for the Qualified Electronic Signature platform, and the migration of reporting to Power BI.
Role
Senior Data Analyst
Stack
KNIME · PostgreSQL
04 — Insurance / InsurTech
Analytics engineering for an insurance client: warehouse medallion architecture layers in BigQuery from raw data to the semantic layer, delivered in a team with an engineering culture.
Focus
Analytics engineering
Stack
BigQuery
05 — Manufacturing (medical devices)
Ten years in EMEA production operations: Power BI and SQL Server reporting for MES and production KPIs, SSIS/VB.NET automation with a team of four engineers, and Lean Manufacturing transformation and transfer projects across several sites.
Role
Support to manager
Stack
Power BI · SQL Server
04 — Contact
A short intro call is enough to see whether and how I can help. Free and direct.
B2B cooperation, invoiced by PlanIT Maksymilian Maciejewski (active VAT payer).
On-site meetings in Poland by prior arrangement. Working languages: Polish and English. Commercial terms are agreed individually.