Poster Nº 00 — CoverSenior Python DeveloperWarsaw · Poland

Hanley

Brian
Donald
Senior Python
Developer

Backend systems, data pipelines and APIs that stay calm under load — written in clean, typed, well-tested Python.

See the works → Get in touch
Brian Donald Hanley
Print 00 / Blue × PinkDuotone
B.D. Hanley — Portfolio Series 2026Ink: Blue / Pink
Poster Nº 01 — StatementAboutEst. 2014

Simple
> Clever

I build the quiet machinery behind products — services, data platforms and APIs that people rely on without ever thinking about them.

For over eleven years I've worked across fintech, logistics and SaaS, taking Python systems from first commit to millions of requests per day. I care about readable code, honest metrics and boring deployments. I lead by reviewing generously, writing things down and leaving every codebase easier to change than I found it.

Print 01Green × Lime
Working principles
Explicit over implicit. Measure before optimising. Tests are documentation that can't lie. Ship small, ship often.
11+Years shipping Python
40+Services in production
9Engineers mentored
import thisInk: Green / Lime
Poster Nº 02 — StackSkills specimenYears in use →

Stack

Language A

  • Python 3.x11
  • asyncio / AnyIO07
  • Type hints · mypy06
  • Pydantic05
  • SQL11
  • Go (services)03
  • Rust via PyO302

Frameworks B

  • Django · DRF10
  • FastAPI05
  • Celery · RQ08
  • SQLAlchemy 2.007
  • pandas · Polars07
  • Airflow · Dagster05
  • pytest · Hypothesis10

Platform C

  • PostgreSQL11
  • Redis · Kafka07
  • Docker · Kubernetes07
  • AWS · GCP08
  • Terraform05
  • GitHub Actions · CI/CD06
  • OpenTelemetry · Grafana04
pip install brian-hanleyInk: Red / Cream
Poster Nº 03 — WorksSelected projects04 prints

Works

  1. 01

    Ledgerline

    Real-time payments ledger · Fintech

    Double-entry ledger service replacing a nightly batch reconciler. Event-sourced on Kafka and PostgreSQL with idempotent FastAPI endpoints and strict decimal handling.

    • FastAPI
    • Kafka
    • PostgreSQL
    • Hypothesis
    4.2ktx / second
  2. 02

    Routewise

    Fleet ETA engine · Logistics

    Delivery time prediction for 1,800 vehicles. Feature pipelines in Polars and Dagster, models served behind an async gateway with p99 under 60 ms.

    • Polars
    • Dagster
    • scikit-learn
    • Redis
    −31%late deliveries
  3. 03

    Tenantry

    Multi-tenant platform · SaaS

    Migrated a Django monolith to schema-per-tenant isolation with zero downtime, plus a permissions layer and audit log adopted by six product teams.

    • Django
    • DRF
    • Celery
    • Kubernetes
    0 minmigration downtime
  4. 04

    pyproof

    Open-source library

    A small contract-testing toolkit for HTTP APIs built on Pydantic models — generate property-based tests straight from your schemas.

    • Pydantic
    • pytest plugin
    • OpenAPI
    1.9kGitHub stars
Sample projects · details under NDA available on requestInk: Pink / Blue
Poster Nº 04 — RecordExperience2014 → Now

The record

A decade of moving from writing features to shaping systems — and from shaping systems to growing the people who build them.

Education
M.Sc. Computer Science
Distributed systems & databases
Languages
English · Polish · German (basic)
  1. 2021 — NowLead role

    Senior Python Developer — Vistula Pay

    • Tech lead for the ledger and payouts domain; team of six.
    • Designed the event-sourced ledger (Ledgerline), cutting reconciliation from 8 h to near real-time.
    • Introduced typed contracts and mypy-strict CI across 14 services.
  2. 2018 — 2021Senior

    Backend Engineer — Northbeam Logistics

    • Built the ETA prediction platform and its data pipelines.
    • Moved batch jobs from cron to Airflow; reduced data incidents by 70%.
  3. 2016 — 2018Mid

    Python Developer — Kestrel SaaS

    • Led the zero-downtime multi-tenant migration of a large Django codebase.
    • Owned the Celery task infrastructure and billing integrations.
  4. 2014 — 2016Junior

    Software Developer — Brightfield Studio

    • Django and Flask web applications for agency clients; first open-source contributions.
References available on requestInk: Lime / Green
Poster Nº 05 — ContactOpen to senior & lead rolesRemote / Warsaw

Hello

Have a Python system that needs to scale, a team that needs a lead, or a codebase that needs untangling? Let's talk.

First name
Brian Donald
Surname
Hanley
Email
tomohirodubreexiyata90@gmail.com
Address
Modlinska 2
03216 Warsaw
Poland
Print 05Red × Cream
Write an email →
© 2026 Brian Donald Hanley · Senior Python DeveloperInk: Red / Cream