David

David Kovalov
Python Backend Developer
[відкрити контакти](див. вище в блоці «контактна інформація») [відкрити контакти](див. вище в блоці «контактна інформація») Lviv @Kevy_D

Summary

Python Backend Developer with 3+ years of experience delivering production backends for AI, logistics,
and marketplace products. Strong in Python, FastAPI/Django, PostgreSQL, asynchronous processing,
third-party integrations, and failure-safe business workflows. Hands-on experience with LLM
orchestration, idempotency, state machines, background workers, subscriptions, payments, testing,
observability, and AWS deployments.

Professional Experience

Python Backend Developer | Posti AI, MyPlanet Design 01/2025 – Present
• Own backend delivery for the content-generation domain in a Python modular monolith, with
separate workers/functions for LLM generation, rendering, webhooks, and scheduled publishing.
• Designed a provider-agnostic LLM orchestration layer with OpenAI as the primary provider and
Gemini fallback for retryable failures; normalized provider errors and validated structured JSON
outputs.
• Implemented idempotency keys and atomic job claiming to prevent duplicate generations, repeated
quota consumption, and double provider charges during mobile retries or worker redelivery.
• Integrated Apple Sign In, App Store subscriptions through RevenueCat webhooks, server-side
entitlement checks, and reconciliation jobs; used Appwrite for account and content persistence.

Python Backend Developer | OYUM Express, MyPlanet Design 02/2024 – 12/2024
• Designed and implemented order, shipment, and parcel modules for a China-to-Kyrgyzstan logistics
flow, including the MarketplaceOrder 1:N Shipments model and normalized carrier tracking events.
• Built a shipment state machine and warehouse workflows for barcode scanning, client-code
matching, weighing, damaged/unmatched parcels, batch consolidation, pickup transfer, and final
handoff.
• Defined transaction boundaries, unique constraints, idempotent upserts, and optimistic locking to
handle duplicate scans, split shipments, and out-of-order events safely.
• Optimized tracking and warehouse queries with PostgreSQL indexes and pagination, and covered
critical flows with integration tests and OpenAPI documentation.

Python Backend Developer | Kova App, MyPlanet Design 02/2023 – 01/2024
• Developed Jobs CRUD, cleaner proposals, profiles, ratings/reviews, REST chat endpoints, basic
notifications, S3 uploads, automated tests, and API documentation.
• Implemented Job Service workflows for hiring and completion, including integration contracts with a
Stripe Connect-backed billing module, access checks, and idempotent state transitions.
• Contributed to WebSocket-based live job/chat updates and RabbitMQ/Celery background
notifications while collaborating through code review and shared API contracts.
Skills

Backend: Python, Asyncio, FastAPI, Django/DRF, Pydantic v2, SQLAlchemy, Django ORM, Alembic
Data: PostgreSQL, PostGIS, Redis, MySQL, MongoDB, pgvector, Qdrant
Architecture & APIs: REST, WebSockets, SSE, Webhooks, gRPC, GraphQL, microservices
Messaging & AI: RabbitMQ, Celery, Kafka, OpenAI API, Gemini API, LLM orchestration, LangChain,
LangGraph, LiteLLM, Langfuse
Cloud & Quality: Docker, Docker Compose, CI/CD, GitHub Actions, AWS (EC2, S3), GCP, Nginx, pytest,
unittest/mock, Prometheus, Grafana, OpenTelemetry, Jaeger
Security & Payments: JWT, OAuth2, RBAC, Apple Sign In, RevenueCat, Stripe

Languages

Ukraine English
C2 B2

Certificates

Claude Docker