Dnipro, Ukraine · Remote-friendly

Serge Zavizion

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

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

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01 · About

Who I Am

Python backend 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» — Master's degree, Computer Engineering (System Programming) (2022–2024)
  • National Metallurgical Academy of Ukraine — Specialist degree (5-year), Automation of Production Processes (2004–2010)

Languages

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

8+
Years of experience
20+
Projects delivered
7
Companies & teams
~50
EV stations managed

02 · Skills

Technical Arsenal

Languages & Frameworks

Python
SQL
Django
Django REST Framework
FastAPI
Flask

Databases

PostgreSQL / PostGIS
MySQL
MongoDB
Redis
SQLite
InfluxDB

APIs & Integrations

OpenAI
ElevenLabs
Stripe
Twilio
Shopify
Google APIs

Async & Queues

Celery
asyncio
WebSockets (Django Channels)
MQTT

Cloud & DevOps

AWS (S3, EC2)
GCP
Docker
Nginx
Linux

Testing, VCS & More

Pytest
Unittest
Git (GitHub, GitLab, Bitbucket)
SQLAlchemy
Shapely
Leaflet
Grafana

03 · Experience

Career Timeline

  1. Jul 2025 – Present

    Python Backend Developer

    Freelance

    Backend development for two production products: a geospatial real-estate platform (Cyprus) and an AI-powered language-learning platform.

    Geospatial real-estate platform — Django, PostGIS

    • Built the parcel data backend: data modeling, spatial queries and admin tooling over 3D MultiPolygon geometries.
    • Built batch ETL pipelines loading Greek cadastral data into PostgreSQL with idempotent upserts (ON CONFLICT) instead of row-by-row inserts.
    • Merged three parcel tables into a single deduplicated source; added map-driven filtering in Django admin with two-way Leaflet ↔ form sync.

    AI language-learning platform — FastAPI, OpenAI, ElevenLabs

    • Cut response time of the core /process-question endpoint by ~45% (9s → 5s) by running OpenAI calls, TTS and history persistence in parallel (AsyncOpenAI + asyncio.gather).
    • Replaced N+1 queries in rules loading with a single batch query; parallelized audio generation with a thread pool and caching.
    • Integrated OpenAI and ElevenLabs for exercise generation and speech synthesis; implemented JWT auth with refresh tokens.
    DjangoPostGISFastAPIOpenAIElevenLabsPostgreSQL

  2. Aug 2024 – Jul 2025

    Python Developer

    Canyon Development

    Control and monitoring systems for a network of ~50 EV charging stations.

    • Designed and built a Flask + MQTT control panel for real-time management of ~50 charging stations: configuration, start/stop, connection status and charge levels.
    • Implemented authentication and role-based access control (admin, operator, technical service).
    • Built an IoT telemetry service ingesting device data over HTTP and WebSocket, storing time series in InfluxDB and visualizing metrics in Grafana.
    • Developed an on-device PyGame/Flask client for LED screens (text, animated banners, QR previews), with GPIO LED indication and ALSA sound notifications managed via systemd/udev.
    • Built declarative network configuration with automatic Wi-Fi/LTE failover.
    FlaskMQTTInfluxDBGrafanaWebSocketsIoT

  3. Jul 2021 – Feb 2024

    Python Developer

    Lunka Technologies

    Outsourcing company. Delivered and maintained four client web projects on Django, DRF, Flask, PostgreSQL and MongoDB.

    • Delivered four client projects end-to-end: new feature development, API design, maintenance, bug fixing and functional testing.
    • Built REST APIs with Django REST Framework to integrate multi-platform applications.
    • Maintained and extended production systems, shipping updates and resolving defects throughout the development lifecycle.
    DjangoDRFPostgreSQLFlaskMongoDB

  4. Mar 2020 – Jul 2021

    Python Developer

    I-CITY

    Software for urban and municipal transport.

    • Developed GPS-tracking systems for urban and municipal transport.
    • Built automated performance-analysis tools for transport operations.
    • Built software for parking terminals.
    DjangoGPSPython

  5. Oct 2019 – Mar 2020

    Python Developer (Freelance)

    DreamTek

    • Built a web platform for freelancers on Django.
    • Integrated Stripe for payment processing.
    DjangoStripe

  6. Feb 2019 – Oct 2019

    Python Software Developer

    SoftServe

    • Developed and optimized a platform automating intangible-asset assessment, reducing time spent on routine tasks for business users.
    • Maintained comprehensive test coverage with PyTest.
    • Worked in an Agile team using Scrum and Jira.
    PythonPytestAgile

  7. Jul 2017 – Feb 2019

    Python Developer

    GoWombat Team

    • Delivered ~10 web and mobile projects end-to-end: e-commerce platforms, CRM systems, ad-monetization and healthcare applications.
    • Built APIs powering mobile application functionality and third-party integrations.
    DjangoREST APIE-commerce

04 · Projects

Selected Work

Geospatial Real-Estate Platform

Under NDA

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

Merged three parcel tables into a single deduplicated source with idempotent upserts (ON CONFLICT) instead of row-by-row inserts.

DjangoPostGISPostgreSQLLeafletETL

AI Language-Learning Platform

Under NDA

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

Cut the core /process-question endpoint by ~45% (9s → 5s) with AsyncOpenAI + asyncio.gather; replaced N+1 queries with a single batch query.

FastAPIOpenAIElevenLabsasyncioJWT

EV Charging Network Control Panel

Under NDA

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

Under NDA

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

Fleet tracking and performance analytics for municipal transport, plus parking terminal software.

DjangoGPSPostgreSQL

05 · Contact

Let's Build Something

Open to remote backend roles and freelance projects: Python, Django, FastAPI, geospatial systems, AI integrations. Based in Dnipro, Ukraine (UTC+2/+3), with good overlap with EU working hours.

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