Dnipro, Ukraine · Remote-friendly

Serge Zavizion

Python Backend Developer — Django · FastAPI · PostgreSQL · AI/LLM

8+ years shipping production web services — from geospatial platforms and IoT fleets to AI-powered products.

01 · About

Who I Am

Python back-end developer with 8+ years building and shipping production web services on Django, DRF, Flask and FastAPI. Strong in PostgreSQL/PostGIS data pipelines, REST API design, and AI/LLM integrations (OpenAI, ElevenLabs). Comfortable owning projects end-to-end — from data modeling and performance tuning to deployment — across web platforms, geospatial systems and IoT.

Education

National Aerospace University «Kharkiv Aviation Institute» — System Programming (2022 — 2024)
National Metallurgical Academy of Ukraine — Automation & Computer-Integrated Technologies (2004 — 2010)

Languages

Ukrainian — Native · English — Upper-Intermediate (B2)

Years of experience

20+

Projects delivered

Companies & teams

Python frameworks

02 · Skills

Technical Arsenal

Languages & Frameworks

Python

Django

Django REST Framework

FastAPI

Flask

Databases

PostgreSQL / PostGIS

MySQL

MongoDB

Redis

SQLite

InfluxDB

APIs & Integrations

OpenAI

ElevenLabs

Stripe

Twilio

Shopify

Google

Async & Queues

Celery

asyncio

WebSockets (Django Channels)

MQTT

Cloud & DevOps

AWS (S3, EC2)

GCP

Docker

Testing, VCS & More

Pytest

Unittest

Git (GitHub, GitLab, Bitbucket)

SQLAlchemy

Shapely

TensorFlow

Grafana

03 · Experience

Career Timeline

July 2025 — Present
Python Developer
Freelance
Backend development across two production projects: a real-estate geospatial platform (Cyprus) and an AI-powered language-learning platform.
- Built geospatial backend on Django + PostGIS for a Cyprus real-estate product: parcel data modeling, spatial queries and admin tooling over MultiPolygon (3D) geometries.
- Engineered ETL pipelines parsing Greek cadastral JSON into PostgreSQL — handled nested structures, BIGINT overflow and deduplication via ON CONFLICT, with batch operations instead of row-by-row loops.
- Implemented dynamic parcel filtering in Django admin with bidirectional Leaflet map ↔ widget synchronization; merged and deduplicated three parcel tables into one clean source.
- On the education platform (FastAPI): cut a core /process-question endpoint from ~9s to ~5s using AsyncOpenAI and asyncio.gather for parallel TTS and history persistence.
- Reduced a rules-loading method from N+1 queries to a single batch query, and parallelized audio generation (ThreadPoolExecutor + caching) in a 1,100-line exercise pipeline.
- Integrated OpenAI and ElevenLabs for dynamic exercise generation and speech synthesis; added JWT auth with refresh tokens and file-based chat history.
DjangoPostGISFastAPIOpenAIElevenLabsPostgreSQL
August 2024 — July 2025
Python Developer
Canyon Development
Production control and monitoring systems for a network of ~50 EV charging stations.
- Designed and built a Flask + MQTT web control panel for centralized, real-time management of ~50 charging stations: configuration, start/stop, connection status and charge levels.
- Added authentication and role-based access control (admin, operator, technical service).
- Implemented an IoT telemetry service ingesting device data over HTTP and WebSocket, storing time series in InfluxDB and visualizing metrics via Grafana dashboards.
- Developed a PyGame/Flask client for on-device LED screens (text, animated banners, QR previews) and managed GPIO-LED indication and ALSA sound notifications via systemd/udev.
- Built declarative network config for automatic Wi-Fi/LTE connectivity with reliable fallback switching between interfaces.
FlaskMQTTInfluxDBGrafanaWebSocketsIoT
July 2021 — February 2024
Software Engineer (Python/Django)
Lunka Technologies
Outsourcing — delivered and maintained 4 client web projects.
- Delivered 4 web projects end-to-end — from new feature development and API design to maintenance, bug fixing and functional testing.
- Built REST APIs (DRF) enabling integration across multi-platform applications.
- Maintained and enhanced existing production sites, resolving defects and shipping updates throughout the development lifecycle.
DjangoDRFPostgreSQLFlaskMongoDB
March 2020 — July 2021
Python (Django) Developer
I-CITY
- Developed GPS-tracking systems and automated performance-analysis tools for urban and municipal transport.
- Built software for parking terminals.
DjangoGPSPython
October 2019 — March 2020
Python (Django) Developer — Freelance
DreamTek
- Built an internet platform for freelancers, integrating Stripe for payment processing.
DjangoStripe
February 2019 — October 2019
Python Software Developer
SoftServe
- Developed and optimized a platform automating intangible-asset assessment, reducing routine task time for business users.
- Worked in Agile (Scrum/JIRA) with comprehensive PyTest coverage.
PythonPytestAgile
July 2017 — February 2019
Python (Django) Developer
GoWombat Team
- Delivered ~10 web and mobile projects end-to-end: e-commerce platforms, CRM systems, ad-monetization and healthcare applications.
- Engineered robust APIs powering mobile application functionality and integrations.
DjangoREST APIE-commerce

04 · Projects

Selected Work

Geospatial Real-Estate Platform

Django + PostGIS backend for a Cyprus real-estate product: parcel data modeling, spatial queries and admin tooling over MultiPolygon (3D) geometries, with ETL pipelines parsing Greek cadastral JSON into PostgreSQL.

Merged three parcel tables into one clean source with batch dedup via ON CONFLICT — no row-by-row loops.

DjangoPostGISPostgreSQLLeafletETL

AI Language-Learning Platform

FastAPI backend with OpenAI and ElevenLabs integrations for dynamic exercise generation and speech synthesis, JWT auth with refresh tokens and chat history.

Cut the core /process-question endpoint from ~9s to ~5s with AsyncOpenAI + asyncio.gather; eliminated N+1 queries in the exercise pipeline.

FastAPIOpenAIElevenLabsasyncioJWT

EV Charging Network Control Panel

Flask + MQTT control panel managing ~50 EV charging stations in real time: configuration, start/stop, connection status and charge levels, with role-based access control.

Centralized management of a distributed IoT fleet with telemetry stored in InfluxDB and live Grafana dashboards.

FlaskMQTTInfluxDBGrafanaRBAC

Urban Transport GPS Tracking

GPS-tracking systems and automated performance-analysis tools for urban and municipal transport, plus software for parking terminals.

Automated performance analysis for municipal transport fleets.

DjangoGPSPostgreSQL

05 · Contact

Let's Build Something

Open to backend roles and freelance projects — Python, Django, FastAPI, geospatial systems, AI integrations. Based in Dnipro, Ukraine, working remotely worldwide.

Email Me