Leonid Chekin
PYTHON BACKEND DEVELOPER · APPLIED AI

I build software
that solves real problems.

Python Backend Developer · commercial experience since 2022

I build APIs, integrations, and AI features for working products. Explore selected case studies, my role, and engineering decisions.

WHAT I BUILD01 — 03
01Backend and APIsFASTAPI / POSTGRESQL / INTEGRATIONS
02AI for documentsRAG / SEARCH / SOURCES
03AutomationTELEGRAM / CRM / WORKFLOWS
PROFILE

From business needs
to working software.

I build backend services, APIs, and integrations in Python, and apply AI where it improves real workflows.

I have worked on commercial Python development since 2022. I also have about 3.5 years of experience in quantitative and algorithmic trading, including market data and time-series analysis. My project work spans requirements, implementation, testing, and delivery.

Since 2022Commercial Python development
BackendAPIs, databases, and integrations
Applied AIRAG, search, and automation
PROJECTS & DEMOS

Explore the projects.

Selected case studies show my role, engineering challenge, and available materials. More projects are listed below.

AI and data processing03

AI News RSS Publisher

Processes full-text RSS feeds, removes semantic duplicates, and prepares Telegram posts with a local language model.

Python / Ollama / Embeddings / PostgreSQL
Source code ↗
Equipment monitoring · MQTT and ML pipeline05

City Sentinel

On the team project, I built the MQTT telemetry path with a central broker, validation, a durable PostgreSQL inbox, InfluxDB persistence, online/offline status, and an ESP32 simulator. Added five-minute aggregation and ML anomaly scoring/alerts. Code is in a project branch; production deployment requires cloud environment configuration.

FastAPI / PostgreSQL / InfluxDB / Docker Compose / Pytest / ML anomaly scoring · MQTT telemetry
Open prototype ↗Open operations demo ↗
Client project · no public demo06

E-commerce payment flow

Implemented the Tilda, T-Bank Acquiring, and ATOL Online integration, including payment-status checks and receipt fiscalization. The client accepted the work; details and source code are confidential.

Payments / Webhooks / API
Commercial experience · no public demo07

AI assistants and integrations

Built incoming-data workflows with semantic deduplication and delivery to CRM and Telegram, plus automation for recurring operations. Project materials are confidential.

Python / APIs / CRM / n8n / Telegram
Personal project · local MVP · 15 modulesN01

ATLAS Studio · business automation platform

My role: built an integrated local MVP with Python/FastAPI/SQLite. One codebase with 15 functional demo modules for lead handling, CRM, booking, knowledge search, CSV/PDF workflows, automation, and analytics. A safe browser showcase uses synthetic data. This is a prototype, not a production SaaS: full authentication, multitenancy, billing, and live integrations are not implemented.

Python / FastAPI / SQLite / REST API / HTML, CSS, JavaScript / Pytest
Open safe showcase ↗
Personal learning project · six demosN02

AI Engineer Portfolio · six demos

My role: built six demonstration FastAPI apps and their shared architecture. Six separate FastAPI apps: lead intake with approval, cited document search, batch file processing, evaluations, monitoring, and safe agent actions. Public demos use SQLite and mock mode; real CRM/email writes and paid model APIs are not connected.

Python / FastAPI / SQLAlchemy / Docker Compose / PostgreSQL + pgvector / Redis + Celery / Render Free
2-minute narrated video tour ↗Try all 6 interactive demos ↗Open demo ↗Swagger API ↗Source code ↗
Personal project · live demoN03

Liniya — lead CRM with a Telegram bot

My role: designed and built the CRM, integrated the Telegram Bot API, and deployed the service. A CRM with a shared lead database, password-protected access, manual entry, search, tags, and statuses. A Telegram bot collects leads step by step and saves them through a webhook. Core flows and a test submission were verified; the project is published as a live demo.

Cloudflare Workers / D1 / JavaScript / Telegram Bot API / Webhooks / SQL
Open demo · no sign-in ↗Manager sign-in ↗Source code ↗Telegram bot ↗
Backend · API prototypeN04

Transfer API · idempotent transfer processing

My role: built the API, storage schema, and event handling. FastAPI service with bearer authentication, PostgreSQL, Alembic migrations, and external_id idempotency enforced by an atomic insert. Signs webhook events with HMAC-SHA256 and retries delivery a bounded number of times. It is not connected to a blockchain or real payment network.

Python / FastAPI / PostgreSQL / Alembic / HMAC-SHA256 / Webhooks
Personal project · prototypeN05

CDL Scout · Telegram group monitoring

My role: built lead collection, filtering, and export. Monitors groups available to an authorized operator, uses local rules to identify potential CDL A / OTR candidates, deduplicates records in SQLite, and exports them to Google Sheets. It does not message candidates; operation requires Telegram credentials and sheet access.

Python / Telegram / SQLite / Google Sheets API
Personal project · temporary demo unavailableN06

AI Support Assistant · Telegram and web support demo

My role: designed and built the Telegram bot, web chat, and backend API. The assistant routes questions, retrieves FAQ answers with PostgreSQL/pgvector, uses conversation context, and hands requests to a human manager. Demo mode runs without an external API key; an OpenAI-compatible LLM can be configured. Includes admin endpoints, Docker Compose, and automated tests. The web link used a temporary tunnel and is currently unavailable.

Python 3.12 / FastAPI / aiogram 3 / SQLAlchemy Async / PostgreSQL + pgvector / RAG / Docker Compose / Pytest / HTML, CSS, JavaScript
Telegram bot ↗
More projects · additional work
Telegram Mini App · opens inside Telegram04

Socialera

A service-ordering MVP with a catalog, balance, transaction history, referrals, and admin workflows. The demo opens inside Telegram, not as a regular website.

Telegram Mini App / API / Database
Launch Mini App · Telegram only ↗Source code ↗
Professional experience · no public results08

Quantitative and algorithmic trading

About 3.5 years working with historical market data, time-series analysis, quantitative calculations, and workflow automation. No public performance or returns are claimed.

Market data / Python / time-series analysis
Unreal Engine · game project09

Nuclear Sunset

A game project developed in Unreal Engine with source files, gameplay mechanics, and environment assets. A public playable build is not currently available.

Unreal Engine / C++ / Blueprints
Interactive browser game12

FASTFO — Echo Range

A game with a moving target, difficulty modes, microphone sound input, and black holes that appear after the target falls.

HTML / CSS / JavaScript / Web Audio
Play the demo ↗
Listings parser · CLI13

HONEX — Avito Parser

Finds new items by product code in Moscow and the surrounding region, removes duplicates, sorts by price, and exports CSV. Includes a reproducible local mode and automated tests; it does not bypass CAPTCHAs or blocks.

Python / HTTP / HTML parsing / CSV / XLSX / unittest
Source code and instructions ↗
CI/CD · DevOps test assignment14

KodStart — Tutor Marketplace

Responsive static demo with GitHub Actions CI/CD: linting, tests, GitHub Pages deployment, and a post-deploy smoke check. An external uptime-monitoring plan is documented, but UptimeRobot is not connected.

HTML / CSS / JavaScript / GitHub Actions / GitHub Pages
Open the demo ↗Source code ↗
TOOLKIT

Technology and engineering practice.

BACKEND & DATA

Backend development

Python · FastAPI · REST API · SQLAlchemy · PostgreSQL · SQLite · Alembic · Redis · Celery · JWT/RBAC · Docker · MQTT · WebSockets

AI & INTEGRATIONS

Search and automation

RAG · Ollama · embeddings · Qdrant · pgvector · Telegram · amoCRM · n8n · Google Sheets · YooKassa · External APIs

QUALITY & DELIVERY

Testing and delivery

Pytest · GitHub Actions · GitLab CI/CD · Prometheus · OpenAPI · Git · Linux · SSH

CONTACT

Looking for a
Python developer?

Backend, integrations, AI search, or automation.

Message me on Telegram ↗